इस पेज का अनुवाद Cloud Translation API से किया गया है.

कर्मचारी शेड्यूलिंग

ऐसे संगठन जिनके कर्मचारी कई शिफ़्ट में काम करते हैं, उन्हें ज़रूरत के मुताबिक शेड्यूल करना होगा हर दिन की शिफ़्ट के लिए कर्मचारी. आम तौर पर, शेड्यूल में कुछ रुकावटें होती हैं. जैसे, "किसी भी कर्मचारी को लगातार दो शिफ़्ट में काम नहीं करना चाहिए". ऐसा शेड्यूल ढूंढा जा रहा है जो सभी कंस्ट्रेंट को पूरा करना मुश्किल हो सकता है.

नीचे दिए गए सेक्शन में, कर्मचारियों के शेड्यूल करने से जुड़ी समस्याओं के दो उदाहरण दिए गए हैं. CP-SAT सॉल्वर का इस्तेमाल करके, उन्हें हल करने का तरीका दिखाना.

बेहतर उदाहरण के लिए, इसे देखें शिफ़्ट शेड्यूलिंग प्रोग्राम GitHub पर.

नर्स शेड्यूल करने से जुड़ी समस्या

अगले उदाहरण में, अस्पताल के सुपरवाइज़र को चार लोगों के लिए एक शेड्यूल बनाना होगा तीन दिन से ज़्यादा समय तक नर्सों के लिए, इन शर्तों को पूरा करना होगा:

हर दिन को आठ घंटे की तीन शिफ़्ट में बांटा जाता है.
हर दिन, हर शिफ़्ट में एक नर्स को असाइन किया जाता है और कोई नर्स ज़्यादा काम करती है एक से ज़्यादा बार बदलें.
हर नर्स को तीन दिनों के दौरान, कम से कम दो शिफ़्ट में काम पर रखा जाता है.

नीचे दिए गए सेक्शन में, नर्स शेड्यूलिंग से जुड़ी समस्याओं का हल बताया गया है.

लाइब्रेरी इंपोर्ट करें

यहां दिया गया कोड ज़रूरी लाइब्रेरी इंपोर्ट करता है.

Python

from ortools.sat.python import cp_model

C++

#include <stdlib.h>

#include <atomic>
#include <map>
#include <numeric>
#include <string>
#include <tuple>
#include <vector>

#include "absl/strings/str_format.h"
#include "ortools/base/logging.h"
#include "ortools/sat/cp_model.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/sat/cp_model_solver.h"
#include "ortools/sat/model.h"
#include "ortools/sat/sat_parameters.pb.h"
#include "ortools/util/time_limit.h"

Java

import com.google.ortools.Loader;
import com.google.ortools.sat.CpModel;
import com.google.ortools.sat.CpSolver;
import com.google.ortools.sat.CpSolverSolutionCallback;
import com.google.ortools.sat.CpSolverStatus;
import com.google.ortools.sat.LinearExpr;
import com.google.ortools.sat.LinearExprBuilder;
import com.google.ortools.sat.Literal;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

C#

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Google.OrTools.Sat;

उदाहरण के लिए डेटा

यह कोड, उदाहरण के लिए डेटा बनाता है.

Python

num_nurses = 4
num_shifts = 3
num_days = 3
all_nurses = range(num_nurses)
all_shifts = range(num_shifts)
all_days = range(num_days)

C++

const int num_nurses = 4;
const int num_shifts = 3;
const int num_days = 3;

std::vector<int> all_nurses(num_nurses);
std::iota(all_nurses.begin(), all_nurses.end(), 0);

std::vector<int> all_shifts(num_shifts);
std::iota(all_shifts.begin(), all_shifts.end(), 0);

std::vector<int> all_days(num_days);
std::iota(all_days.begin(), all_days.end(), 0);

Java

final int numNurses = 4;
final int numDays = 3;
final int numShifts = 3;

final int[] allNurses = IntStream.range(0, numNurses).toArray();
final int[] allDays = IntStream.range(0, numDays).toArray();
final int[] allShifts = IntStream.range(0, numShifts).toArray();

C#

const int numNurses = 4;
const int numDays = 3;
const int numShifts = 3;

int[] allNurses = Enumerable.Range(0, numNurses).ToArray();
int[] allDays = Enumerable.Range(0, numDays).ToArray();
int[] allShifts = Enumerable.Range(0, numShifts).ToArray();

मॉडल बनाना

यह कोड मॉडल बनाता है.

Python

model = cp_model.CpModel()

C++

CpModelBuilder cp_model;

Java

CpModel model = new CpModel();

C#

CpModel model = new CpModel();
model.Model.Variables.Capacity = numNurses * numDays * numShifts;

वैरिएबल बनाना

यह कोड, वैरिएबल का एक कलेक्शन बनाता है.

Python

shifts = {}
for n in all_nurses:
    for d in all_days:
        for s in all_shifts:
            shifts[(n, d, s)] = model.new_bool_var(f"shift_n{n}_d{d}_s{s}")

C++

std::map<std::tuple<int, int, int>, BoolVar> shifts;
for (int n : all_nurses) {
  for (int d : all_days) {
    for (int s : all_shifts) {
      auto key = std::make_tuple(n, d, s);
      shifts[key] = cp_model.NewBoolVar().WithName(
          absl::StrFormat("shift_n%dd%ds%d", n, d, s));
    }
  }
}

Java

Literal[][][] shifts = new Literal[numNurses][numDays][numShifts];
for (int n : allNurses) {
  for (int d : allDays) {
    for (int s : allShifts) {
      shifts[n][d][s] = model.newBoolVar("shifts_n" + n + "d" + d + "s" + s);
    }
  }
}

C#

Dictionary<(int, int, int), BoolVar> shifts =
    new Dictionary<(int, int, int), BoolVar>(numNurses * numDays * numShifts);
foreach (int n in allNurses)
{
    foreach (int d in allDays)
    {
        foreach (int s in allShifts)
        {
            shifts.Add((n, d, s), model.NewBoolVar($"shifts_n{n}d{d}s{s}"));
        }
    }
}

कलेक्शन में, नर्सों को शिफ़्ट करने के लिए असाइनमेंट इस तरह परिभाषित किए गए हैं: अगर d दिन को नर्स को shift s असाइन किया गया है, तो shifts[(n, d, s)] का मान 1 होता है. साथ ही, 0 के बराबर होता है नहीं तो.

नर्सों को शिफ़्ट में असाइन करें

इसके बाद, हम आपको नर्सों को शिफ़्ट में असाइन करने का तरीका बताते हैं, जो इन पाबंदियों के हिसाब से होते हैं:

हर शिफ़्ट में हर दिन एक नर्स को असाइन किया जाता है.
हर नर्स एक दिन में ज़्यादा से ज़्यादा एक शिफ़्ट में काम करती है.

पहली शर्त बनाने वाला कोड यहां दिया गया है.

Python

for d in all_days:
    for s in all_shifts:
        model.add_exactly_one(shifts[(n, d, s)] for n in all_nurses)

C++

for (int d : all_days) {
  for (int s : all_shifts) {
    std::vector<BoolVar> nurses;
    for (int n : all_nurses) {
      auto key = std::make_tuple(n, d, s);
      nurses.push_back(shifts[key]);
    }
    cp_model.AddExactlyOne(nurses);
  }
}

Java

for (int d : allDays) {
  for (int s : allShifts) {
    List<Literal> nurses = new ArrayList<>();
    for (int n : allNurses) {
      nurses.add(shifts[n][d][s]);
    }
    model.addExactlyOne(nurses);
  }
}

C#

List<ILiteral> literals = new List<ILiteral>();
foreach (int d in allDays)
{
    foreach (int s in allShifts)
    {
        foreach (int n in allNurses)
        {
            literals.Add(shifts[(n, d, s)]);
        }
        model.AddExactlyOne(literals);
        literals.Clear();
    }
}

आखिरी लाइन में यह बताया गया है कि हर शिफ़्ट के लिए, असाइन की गई नर्स की कुल संख्या shift 1 है.

इसके बाद, यहां एक कोड दिया गया है. इसके मुताबिक, यह ज़रूरी है कि हर नर्स ज़्यादा से ज़्यादा एक शिफ़्ट में काम करे दिन.

Python

for n in all_nurses:
    for d in all_days:
        model.add_at_most_one(shifts[(n, d, s)] for s in all_shifts)

C++

for (int n : all_nurses) {
  for (int d : all_days) {
    std::vector<BoolVar> work;
    for (int s : all_shifts) {
      auto key = std::make_tuple(n, d, s);
      work.push_back(shifts[key]);
    }
    cp_model.AddAtMostOne(work);
  }
}

Java

for (int n : allNurses) {
  for (int d : allDays) {
    List<Literal> work = new ArrayList<>();
    for (int s : allShifts) {
      work.add(shifts[n][d][s]);
    }
    model.addAtMostOne(work);
  }
}

C#

foreach (int n in allNurses)
{
    foreach (int d in allDays)
    {
        foreach (int s in allShifts)
        {
            literals.Add(shifts[(n, d, s)]);
        }
        model.AddAtMostOne(literals);
        literals.Clear();
    }
}

हर नर्स के लिए, असाइन की गई शिफ़्ट का कुल योग 1 होता है ("ज़्यादा से ज़्यादा" क्योंकि नर्स के पास आज की छुट्टी भी हो सकती है).

शिफ़्ट समान रूप से असाइन करें

इसके बाद, हम आपको बताएंगे कि नर्सों को समान रूप से शिफ़्ट असाइन कैसे करें. तीन दिनों में नौ बार तापमान में बदलाव होता है. इसलिए, हम दो शिफ़्ट असाइन कर सकते हैं चारों नर्स में से हर एक को. इसके बाद, एक शिफ़्ट बाकी होगी, जिसे किसी भी नर्स को असाइन किया जा सकता है.

यहां दिए गए कोड से पक्का होता है कि हर नर्स तीन दिनों की अवधि है.

Python

# Try to distribute the shifts evenly, so that each nurse works
# min_shifts_per_nurse shifts. If this is not possible, because the total
# number of shifts is not divisible by the number of nurses, some nurses will
# be assigned one more shift.
min_shifts_per_nurse = (num_shifts * num_days) // num_nurses
if num_shifts * num_days % num_nurses == 0:
    max_shifts_per_nurse = min_shifts_per_nurse
else:
    max_shifts_per_nurse = min_shifts_per_nurse + 1
for n in all_nurses:
    shifts_worked = []
    for d in all_days:
        for s in all_shifts:
            shifts_worked.append(shifts[(n, d, s)])
    model.add(min_shifts_per_nurse <= sum(shifts_worked))
    model.add(sum(shifts_worked) <= max_shifts_per_nurse)

C++

// Try to distribute the shifts evenly, so that each nurse works
// min_shifts_per_nurse shifts. If this is not possible, because the total
// number of shifts is not divisible by the number of nurses, some nurses will
// be assigned one more shift.
int min_shifts_per_nurse = (num_shifts * num_days) / num_nurses;
int max_shifts_per_nurse;
if ((num_shifts * num_days) % num_nurses == 0) {
  max_shifts_per_nurse = min_shifts_per_nurse;
} else {
  max_shifts_per_nurse = min_shifts_per_nurse + 1;
}
for (int n : all_nurses) {
  std::vector<BoolVar> shifts_worked;
  for (int d : all_days) {
    for (int s : all_shifts) {
      auto key = std::make_tuple(n, d, s);
      shifts_worked.push_back(shifts[key]);
    }
  }
  cp_model.AddLessOrEqual(min_shifts_per_nurse,
                          LinearExpr::Sum(shifts_worked));
  cp_model.AddLessOrEqual(LinearExpr::Sum(shifts_worked),
                          max_shifts_per_nurse);
}

Java

// Try to distribute the shifts evenly, so that each nurse works
// minShiftsPerNurse shifts. If this is not possible, because the total
// number of shifts is not divisible by the number of nurses, some nurses will
// be assigned one more shift.
int minShiftsPerNurse = (numShifts * numDays) / numNurses;
int maxShiftsPerNurse;
if ((numShifts * numDays) % numNurses == 0) {
  maxShiftsPerNurse = minShiftsPerNurse;
} else {
  maxShiftsPerNurse = minShiftsPerNurse + 1;
}
for (int n : allNurses) {
  LinearExprBuilder shiftsWorked = LinearExpr.newBuilder();
  for (int d : allDays) {
    for (int s : allShifts) {
      shiftsWorked.add(shifts[n][d][s]);
    }
  }
  model.addLinearConstraint(shiftsWorked, minShiftsPerNurse, maxShiftsPerNurse);
}

C#

// Try to distribute the shifts evenly, so that each nurse works
// minShiftsPerNurse shifts. If this is not possible, because the total
// number of shifts is not divisible by the number of nurses, some nurses will
// be assigned one more shift.
int minShiftsPerNurse = (numShifts * numDays) / numNurses;
int maxShiftsPerNurse;
if ((numShifts * numDays) % numNurses == 0)
{
    maxShiftsPerNurse = minShiftsPerNurse;
}
else
{
    maxShiftsPerNurse = minShiftsPerNurse + 1;
}

List<IntVar> shiftsWorked = new List<IntVar>();
foreach (int n in allNurses)
{
    foreach (int d in allDays)
    {
        foreach (int s in allShifts)
        {
            shiftsWorked.Add(shifts[(n, d, s)]);
        }
    }
    model.AddLinearConstraint(LinearExpr.Sum(shiftsWorked), minShiftsPerNurse, maxShiftsPerNurse);
    shiftsWorked.Clear();
}

शेड्यूल की अवधि में कुल num_shifts * num_days शिफ़्ट की गई हैं. इसलिए, आपके कम से कम (num_shifts * num_days) // num_nurses असाइन कर सकते हैं

हर नर्स में शिफ़्ट हो जाता है, लेकिन हो सकता है कि कुछ शिफ़्ट बचा हो. (यहां // Python है पूर्णांक विभाजन ऑपरेटर, जो सामान्य भागफल का फ़्लोर लौटाता है.)

num_nurses = 4, num_shifts = 3, और num_days = 3 की दी गई वैल्यू के लिए, एक्सप्रेशन min_shifts_per_nurse का मान (3 * 3 // 4) = 2 है, इसलिए आपको हर नर्स को कम से कम दो शिफ़्ट असाइन कर सकते हैं. यह इस नियम के तहत तय किया जाता है: कंस्ट्रेंट (यहां Python में)

model.add(min_shifts_per_nurse <= sum(shifts_worked))

अभी तक किसी भी व्यक्ति ने चेक इन नहीं किया है

तीन दिनों के दौरान कुल नौ शिफ़्ट हुए हैं. इसलिए, एक इसके बाद, बाकी शिफ़्ट होने में मदद मिलेगी. अतिरिक्त बदलाव इनमें से कोई भी हो सकता है असाइन किया जा सकता है.

आखिरी लाइन (यहां Python में)

model.add(sum(shifts_worked) <= max_shifts_per_nurse)

यह पक्का करता है कि किसी भी नर्स को एक से ज़्यादा शिफ़्ट के लिए असाइन किया गया हो.

इस मामले में कंस्ट्रेंट ज़रूरी नहीं है, क्योंकि सिर्फ़ एक अतिरिक्त shift. हालांकि, अलग-अलग पैरामीटर वैल्यू के लिए, कई और बदलाव हो सकते हैं, जिस मामले में कंस्ट्रेंट ज़रूरी होता है.

सॉल्वर पैरामीटर अपडेट करना

नॉन-ऑप्टिमाइज़ेशन मॉडल में, सभी समाधानों के लिए खोज की सुविधा चालू की जा सकती है.

Python

solver = cp_model.CpSolver()
solver.parameters.linearization_level = 0
# Enumerate all solutions.
solver.parameters.enumerate_all_solutions = True

C++

Model model;
SatParameters parameters;
parameters.set_linearization_level(0);
// Enumerate all solutions.
parameters.set_enumerate_all_solutions(true);
model.Add(NewSatParameters(parameters));

Java

CpSolver solver = new CpSolver();
solver.getParameters().setLinearizationLevel(0);
// Tell the solver to enumerate all solutions.
solver.getParameters().setEnumerateAllSolutions(true);

C#

CpSolver solver = new CpSolver();
// Tell the solver to enumerate all solutions.
solver.StringParameters += "linearization_level:0 " + "enumerate_all_solutions:true ";

समाधान कॉलबैक रजिस्टर करें

आपको सॉल्वर पर एक कॉलबैक रजिस्टर करना होगा, जिसे हर समाधान.

Python

class NursesPartialSolutionPrinter(cp_model.CpSolverSolutionCallback):
    """Print intermediate solutions."""

    def __init__(self, shifts, num_nurses, num_days, num_shifts, limit):
        cp_model.CpSolverSolutionCallback.__init__(self)
        self._shifts = shifts
        self._num_nurses = num_nurses
        self._num_days = num_days
        self._num_shifts = num_shifts
        self._solution_count = 0
        self._solution_limit = limit

    def on_solution_callback(self):
        self._solution_count += 1
        print(f"Solution {self._solution_count}")
        for d in range(self._num_days):
            print(f"Day {d}")
            for n in range(self._num_nurses):
                is_working = False
                for s in range(self._num_shifts):
                    if self.value(self._shifts[(n, d, s)]):
                        is_working = True
                        print(f"  Nurse {n} works shift {s}")
                if not is_working:
                    print(f"  Nurse {n} does not work")
        if self._solution_count >= self._solution_limit:
            print(f"Stop search after {self._solution_limit} solutions")
            self.stop_search()

    def solutionCount(self):
        return self._solution_count

# Display the first five solutions.
solution_limit = 5
solution_printer = NursesPartialSolutionPrinter(
    shifts, num_nurses, num_days, num_shifts, solution_limit
)

C++

// Create an atomic Boolean that will be periodically checked by the limit.
std::atomic<bool> stopped(false);
model.GetOrCreate<TimeLimit>()->RegisterExternalBooleanAsLimit(&stopped);

const int kSolutionLimit = 5;
int num_solutions = 0;
model.Add(NewFeasibleSolutionObserver([&](const CpSolverResponse& r) {
  LOG(INFO) << "Solution " << num_solutions;
  for (int d : all_days) {
    LOG(INFO) << "Day " << std::to_string(d);
    for (int n : all_nurses) {
      bool is_working = false;
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        if (SolutionIntegerValue(r, shifts[key])) {
          is_working = true;
          LOG(INFO) << "  Nurse " << std::to_string(n) << " works shift "
                    << std::to_string(s);
        }
      }
      if (!is_working) {
        LOG(INFO) << "  Nurse " << std::to_string(n) << " does not work";
      }
    }
  }
  num_solutions++;
  if (num_solutions >= kSolutionLimit) {
    stopped = true;
    LOG(INFO) << "Stop search after " << kSolutionLimit << " solutions.";
  }
}));

Java

final int solutionLimit = 5;
class VarArraySolutionPrinterWithLimit extends CpSolverSolutionCallback {
  public VarArraySolutionPrinterWithLimit(
      int[] allNurses, int[] allDays, int[] allShifts, Literal[][][] shifts, int limit) {
    solutionCount = 0;
    this.allNurses = allNurses;
    this.allDays = allDays;
    this.allShifts = allShifts;
    this.shifts = shifts;
    solutionLimit = limit;
  }

  @Override
  public void onSolutionCallback() {
    System.out.printf("Solution #%d:%n", solutionCount);
    for (int d : allDays) {
      System.out.printf("Day %d%n", d);
      for (int n : allNurses) {
        boolean isWorking = false;
        for (int s : allShifts) {
          if (booleanValue(shifts[n][d][s])) {
            isWorking = true;
            System.out.printf("  Nurse %d work shift %d%n", n, s);
          }
        }
        if (!isWorking) {
          System.out.printf("  Nurse %d does not work%n", n);
        }
      }
    }
    solutionCount++;
    if (solutionCount >= solutionLimit) {
      System.out.printf("Stop search after %d solutions%n", solutionLimit);
      stopSearch();
    }
  }

  public int getSolutionCount() {
    return solutionCount;
  }

  private int solutionCount;
  private final int[] allNurses;
  private final int[] allDays;
  private final int[] allShifts;
  private final Literal[][][] shifts;
  private final int solutionLimit;
}

VarArraySolutionPrinterWithLimit cb =
    new VarArraySolutionPrinterWithLimit(allNurses, allDays, allShifts, shifts, solutionLimit);

C#

पहले SolutionPrinter क्लास तय करें.

public class SolutionPrinter : CpSolverSolutionCallback
{
    public SolutionPrinter(int[] allNurses, int[] allDays, int[] allShifts,
                           Dictionary<(int, int, int), BoolVar> shifts, int limit)
    {
        solutionCount_ = 0;
        allNurses_ = allNurses;
        allDays_ = allDays;
        allShifts_ = allShifts;
        shifts_ = shifts;
        solutionLimit_ = limit;
    }

    public override void OnSolutionCallback()
    {
        Console.WriteLine($"Solution #{solutionCount_}:");
        foreach (int d in allDays_)
        {
            Console.WriteLine($"Day {d}");
            foreach (int n in allNurses_)
            {
                bool isWorking = false;
                foreach (int s in allShifts_)
                {
                    if (Value(shifts_[(n, d, s)]) == 1L)
                    {
                        isWorking = true;
                        Console.WriteLine($"  Nurse {n} work shift {s}");
                    }
                }
                if (!isWorking)
                {
                    Console.WriteLine($"  Nurse {d} does not work");
                }
            }
        }
        solutionCount_++;
        if (solutionCount_ >= solutionLimit_)
        {
            Console.WriteLine($"Stop search after {solutionLimit_} solutions");
            StopSearch();
        }
    }

    public int SolutionCount()
    {
        return solutionCount_;
    }

    private int solutionCount_;
    private int[] allNurses_;
    private int[] allDays_;
    private int[] allShifts_;
    private Dictionary<(int, int, int), BoolVar> shifts_;
    private int solutionLimit_;
}

अभी तक किसी भी व्यक्ति ने चेक इन नहीं किया है फिर इसका उपयोग करके इसे इंस्टैंशिएट करें:

const int solutionLimit = 5;
SolutionPrinter cb = new SolutionPrinter(allNurses, allDays, allShifts, shifts, solutionLimit);

सॉल्वर आज़माएं

नीचे दिया गया कोड, सॉल्वर को कॉल करता है और पहले पांच सलूशन को दिखाता है.

Python

solver.solve(model, solution_printer)

C++

const CpSolverResponse response = SolveCpModel(cp_model.Build(), &model);

Java

CpSolverStatus status = solver.solve(model, cb);
System.out.println("Status: " + status);
System.out.println(cb.getSolutionCount() + " solutions found.");

C#

CpSolverStatus status = solver.Solve(model, cb);
Console.WriteLine($"Solve status: {status}");

समाधान

ये रहे पहले पाँच समाधान.

Solution 0
Day 0
Nurse 0 does not work
Nurse 1 works shift 0
Nurse 2 works shift 1
Nurse 3 works shift 2
Day 1
Nurse 0 works shift 2
Nurse 1 does not work
Nurse 2 works shift 1
Nurse 3 works shift 0
Day 2
Nurse 0 works shift 2
Nurse 1 works shift 1
Nurse 2 works shift 0
Nurse 3 does not work

Solution 1
Day 0
Nurse 0 works shift 0
Nurse 1 does not work
Nurse 2 works shift 1
Nurse 3 works shift 2
Day 1
Nurse 0 does not work
Nurse 1 works shift 2
Nurse 2 works shift 1
Nurse 3 works shift 0
Day 2
Nurse 0 works shift 2
Nurse 1 works shift 1
Nurse 2 works shift 0
Nurse 3 does not work

Solution 2
Day 0 Nurse 0 works shift 0
Nurse 1 does not work
Nurse 2 works shift 1
Nurse 3 works shift 2
Day 1
Nurse 0 works shift 1
Nurse 1 works shift 2
Nurse 2 does not work
Nurse 3 works shift 0
Day 2
Nurse 0 works shift 2
Nurse 1 works shift 1
Nurse 2 works shift 0
Nurse 3 does not work

Solution 3
Day 0 Nurse 0 does not work
Nurse 1 works shift 0
Nurse 2 works shift 1
Nurse 3 works shift 2
Day 1
Nurse 0 works shift 1
Nurse 1 works shift 2
Nurse 2 does not work
Nurse 3 works shift 0
Day 2
Nurse 0 works shift 2
Nurse 1 works shift 1
Nurse 2 works shift 0
Nurse 3 does not work

Solution 4
Day 0
Nurse 0 does not work
Nurse 1 works shift 0
Nurse 2 works shift 1
Nurse 3 works shift 2
Day 1
Nurse 0 works shift 2
Nurse 1 works shift 1
Nurse 2 does not work
Nurse 3 works shift 0
Day 2
Nurse 0 works shift 2
Nurse 1 works shift 1
Nurse 2 works shift 0
Nurse 3 does not work

Statistics
  - conflicts      : 5
  - branches       : 142
  - wall time      : 0.002484 s
  - solutions found: 5

समाधान की कुल संख्या 5184 है. यह गिनती करने का तर्क इसकी वजह बताता है.

सबसे पहले, उस नर्स के लिए चार विकल्प हैं जो अतिरिक्त शिफ़्ट में काम करती है. इस नर्स को चुनने के बाद, उस नर्स को तीन शिफ़्ट में असाइन किया जा सकता है असाइन करने के संभावित तरीकों की संख्या बताई गई है. अतिरिक्त शिफ़्ट 4 · 3³ = 108 है. इस नर्स को असाइन किए जाने के बाद, हर दिन दो असाइन नहीं की गईं शिफ़्ट होती हैं.

बाकी तीन नर्स में से, एक कामकाजी दिन 0 और 1, एक कामकाजी दिन 0 और 2 है. और एक कामकाजी दिन, पहले और दूसरे दिन के लिए. तीन जवाब हैं! = इन दिनों में नर्सों को काम असाइन करने के छह तरीके डायग्राम नीचे दिया गया है. (तीन नर्स को A, B, और C लेबल में रखा गया है. हालांकि, हमने अभी तक असाइन किया गया हो.)

Day 0    Day 1    Day 2
 A B      A C      B C
 A B      B C      A C
 A C      A B      B C
 A C      B C      A B
 B C      A B      A C
 B C      A C      A B

ऊपर दिए गए डायग्राम में मौजूद हर लाइन के लिए, 2³ = आठ नतीजे हो सकते हैं बाकी शिफ़्ट, नर्सों को असाइन करें. हर दिन दो विकल्प चुनें. इसलिए, संभावित असाइनमेंट की कुल संख्या 108·6·8 = 5184 है.

पूरा प्रोग्राम

नर्स शेड्यूलिंग समस्या के लिए पूरा कार्यक्रम यहां दिया गया है.

Python

"""Example of a simple nurse scheduling problem."""
from ortools.sat.python import cp_model


def main() -> None:
    # Data.
    num_nurses = 4
    num_shifts = 3
    num_days = 3
    all_nurses = range(num_nurses)
    all_shifts = range(num_shifts)
    all_days = range(num_days)

    # Creates the model.
    model = cp_model.CpModel()

    # Creates shift variables.
    # shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
    shifts = {}
    for n in all_nurses:
        for d in all_days:
            for s in all_shifts:
                shifts[(n, d, s)] = model.new_bool_var(f"shift_n{n}_d{d}_s{s}")

    # Each shift is assigned to exactly one nurse in the schedule period.
    for d in all_days:
        for s in all_shifts:
            model.add_exactly_one(shifts[(n, d, s)] for n in all_nurses)

    # Each nurse works at most one shift per day.
    for n in all_nurses:
        for d in all_days:
            model.add_at_most_one(shifts[(n, d, s)] for s in all_shifts)

    # Try to distribute the shifts evenly, so that each nurse works
    # min_shifts_per_nurse shifts. If this is not possible, because the total
    # number of shifts is not divisible by the number of nurses, some nurses will
    # be assigned one more shift.
    min_shifts_per_nurse = (num_shifts * num_days) // num_nurses
    if num_shifts * num_days % num_nurses == 0:
        max_shifts_per_nurse = min_shifts_per_nurse
    else:
        max_shifts_per_nurse = min_shifts_per_nurse + 1
    for n in all_nurses:
        shifts_worked = []
        for d in all_days:
            for s in all_shifts:
                shifts_worked.append(shifts[(n, d, s)])
        model.add(min_shifts_per_nurse <= sum(shifts_worked))
        model.add(sum(shifts_worked) <= max_shifts_per_nurse)

    # Creates the solver and solve.
    solver = cp_model.CpSolver()
    solver.parameters.linearization_level = 0
    # Enumerate all solutions.
    solver.parameters.enumerate_all_solutions = True

    class NursesPartialSolutionPrinter(cp_model.CpSolverSolutionCallback):
        """Print intermediate solutions."""

        def __init__(self, shifts, num_nurses, num_days, num_shifts, limit):
            cp_model.CpSolverSolutionCallback.__init__(self)
            self._shifts = shifts
            self._num_nurses = num_nurses
            self._num_days = num_days
            self._num_shifts = num_shifts
            self._solution_count = 0
            self._solution_limit = limit

        def on_solution_callback(self):
            self._solution_count += 1
            print(f"Solution {self._solution_count}")
            for d in range(self._num_days):
                print(f"Day {d}")
                for n in range(self._num_nurses):
                    is_working = False
                    for s in range(self._num_shifts):
                        if self.value(self._shifts[(n, d, s)]):
                            is_working = True
                            print(f"  Nurse {n} works shift {s}")
                    if not is_working:
                        print(f"  Nurse {n} does not work")
            if self._solution_count >= self._solution_limit:
                print(f"Stop search after {self._solution_limit} solutions")
                self.stop_search()

        def solutionCount(self):
            return self._solution_count

    # Display the first five solutions.
    solution_limit = 5
    solution_printer = NursesPartialSolutionPrinter(
        shifts, num_nurses, num_days, num_shifts, solution_limit
    )

    solver.solve(model, solution_printer)

    # Statistics.
    print("\nStatistics")
    print(f"  - conflicts      : {solver.num_conflicts}")
    print(f"  - branches       : {solver.num_branches}")
    print(f"  - wall time      : {solver.wall_time} s")
    print(f"  - solutions found: {solution_printer.solutionCount()}")


if __name__ == "__main__":
    main()

C++

// Example of a simple nurse scheduling problem.
#include <stdlib.h>

#include <atomic>
#include <map>
#include <numeric>
#include <string>
#include <tuple>
#include <vector>

#include "absl/strings/str_format.h"
#include "ortools/base/logging.h"
#include "ortools/sat/cp_model.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/sat/cp_model_solver.h"
#include "ortools/sat/model.h"
#include "ortools/sat/sat_parameters.pb.h"
#include "ortools/util/time_limit.h"

namespace operations_research {
namespace sat {

void NurseSat() {
  const int num_nurses = 4;
  const int num_shifts = 3;
  const int num_days = 3;

  std::vector<int> all_nurses(num_nurses);
  std::iota(all_nurses.begin(), all_nurses.end(), 0);

  std::vector<int> all_shifts(num_shifts);
  std::iota(all_shifts.begin(), all_shifts.end(), 0);

  std::vector<int> all_days(num_days);
  std::iota(all_days.begin(), all_days.end(), 0);

  // Creates the model.
  CpModelBuilder cp_model;

  // Creates shift variables.
  // shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
  std::map<std::tuple<int, int, int>, BoolVar> shifts;
  for (int n : all_nurses) {
    for (int d : all_days) {
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        shifts[key] = cp_model.NewBoolVar().WithName(
            absl::StrFormat("shift_n%dd%ds%d", n, d, s));
      }
    }
  }

  // Each shift is assigned to exactly one nurse in the schedule period.
  for (int d : all_days) {
    for (int s : all_shifts) {
      std::vector<BoolVar> nurses;
      for (int n : all_nurses) {
        auto key = std::make_tuple(n, d, s);
        nurses.push_back(shifts[key]);
      }
      cp_model.AddExactlyOne(nurses);
    }
  }

  // Each nurse works at most one shift per day.
  for (int n : all_nurses) {
    for (int d : all_days) {
      std::vector<BoolVar> work;
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        work.push_back(shifts[key]);
      }
      cp_model.AddAtMostOne(work);
    }
  }

  // Try to distribute the shifts evenly, so that each nurse works
  // min_shifts_per_nurse shifts. If this is not possible, because the total
  // number of shifts is not divisible by the number of nurses, some nurses will
  // be assigned one more shift.
  int min_shifts_per_nurse = (num_shifts * num_days) / num_nurses;
  int max_shifts_per_nurse;
  if ((num_shifts * num_days) % num_nurses == 0) {
    max_shifts_per_nurse = min_shifts_per_nurse;
  } else {
    max_shifts_per_nurse = min_shifts_per_nurse + 1;
  }
  for (int n : all_nurses) {
    std::vector<BoolVar> shifts_worked;
    for (int d : all_days) {
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        shifts_worked.push_back(shifts[key]);
      }
    }
    cp_model.AddLessOrEqual(min_shifts_per_nurse,
                            LinearExpr::Sum(shifts_worked));
    cp_model.AddLessOrEqual(LinearExpr::Sum(shifts_worked),
                            max_shifts_per_nurse);
  }

  Model model;
  SatParameters parameters;
  parameters.set_linearization_level(0);
  // Enumerate all solutions.
  parameters.set_enumerate_all_solutions(true);
  model.Add(NewSatParameters(parameters));

  // Display the first five solutions.
  // Create an atomic Boolean that will be periodically checked by the limit.
  std::atomic<bool> stopped(false);
  model.GetOrCreate<TimeLimit>()->RegisterExternalBooleanAsLimit(&stopped);

  const int kSolutionLimit = 5;
  int num_solutions = 0;
  model.Add(NewFeasibleSolutionObserver([&](const CpSolverResponse& r) {
    LOG(INFO) << "Solution " << num_solutions;
    for (int d : all_days) {
      LOG(INFO) << "Day " << std::to_string(d);
      for (int n : all_nurses) {
        bool is_working = false;
        for (int s : all_shifts) {
          auto key = std::make_tuple(n, d, s);
          if (SolutionIntegerValue(r, shifts[key])) {
            is_working = true;
            LOG(INFO) << "  Nurse " << std::to_string(n) << " works shift "
                      << std::to_string(s);
          }
        }
        if (!is_working) {
          LOG(INFO) << "  Nurse " << std::to_string(n) << " does not work";
        }
      }
    }
    num_solutions++;
    if (num_solutions >= kSolutionLimit) {
      stopped = true;
      LOG(INFO) << "Stop search after " << kSolutionLimit << " solutions.";
    }
  }));

  const CpSolverResponse response = SolveCpModel(cp_model.Build(), &model);

  // Statistics.
  LOG(INFO) << "Statistics";
  LOG(INFO) << CpSolverResponseStats(response);
  LOG(INFO) << "solutions found : " << std::to_string(num_solutions);
}

}  // namespace sat
}  // namespace operations_research

int main() {
  operations_research::sat::NurseSat();
  return EXIT_SUCCESS;
}

Java

package com.google.ortools.sat.samples;
import com.google.ortools.Loader;
import com.google.ortools.sat.CpModel;
import com.google.ortools.sat.CpSolver;
import com.google.ortools.sat.CpSolverSolutionCallback;
import com.google.ortools.sat.CpSolverStatus;
import com.google.ortools.sat.LinearExpr;
import com.google.ortools.sat.LinearExprBuilder;
import com.google.ortools.sat.Literal;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

/** Nurses problem. */
public class NursesSat {
  public static void main(String[] args) {
    Loader.loadNativeLibraries();
    final int numNurses = 4;
    final int numDays = 3;
    final int numShifts = 3;

    final int[] allNurses = IntStream.range(0, numNurses).toArray();
    final int[] allDays = IntStream.range(0, numDays).toArray();
    final int[] allShifts = IntStream.range(0, numShifts).toArray();

    // Creates the model.
    CpModel model = new CpModel();

    // Creates shift variables.
    // shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
    Literal[][][] shifts = new Literal[numNurses][numDays][numShifts];
    for (int n : allNurses) {
      for (int d : allDays) {
        for (int s : allShifts) {
          shifts[n][d][s] = model.newBoolVar("shifts_n" + n + "d" + d + "s" + s);
        }
      }
    }

    // Each shift is assigned to exactly one nurse in the schedule period.
    for (int d : allDays) {
      for (int s : allShifts) {
        List<Literal> nurses = new ArrayList<>();
        for (int n : allNurses) {
          nurses.add(shifts[n][d][s]);
        }
        model.addExactlyOne(nurses);
      }
    }

    // Each nurse works at most one shift per day.
    for (int n : allNurses) {
      for (int d : allDays) {
        List<Literal> work = new ArrayList<>();
        for (int s : allShifts) {
          work.add(shifts[n][d][s]);
        }
        model.addAtMostOne(work);
      }
    }

    // Try to distribute the shifts evenly, so that each nurse works
    // minShiftsPerNurse shifts. If this is not possible, because the total
    // number of shifts is not divisible by the number of nurses, some nurses will
    // be assigned one more shift.
    int minShiftsPerNurse = (numShifts * numDays) / numNurses;
    int maxShiftsPerNurse;
    if ((numShifts * numDays) % numNurses == 0) {
      maxShiftsPerNurse = minShiftsPerNurse;
    } else {
      maxShiftsPerNurse = minShiftsPerNurse + 1;
    }
    for (int n : allNurses) {
      LinearExprBuilder shiftsWorked = LinearExpr.newBuilder();
      for (int d : allDays) {
        for (int s : allShifts) {
          shiftsWorked.add(shifts[n][d][s]);
        }
      }
      model.addLinearConstraint(shiftsWorked, minShiftsPerNurse, maxShiftsPerNurse);
    }

    CpSolver solver = new CpSolver();
    solver.getParameters().setLinearizationLevel(0);
    // Tell the solver to enumerate all solutions.
    solver.getParameters().setEnumerateAllSolutions(true);

    // Display the first five solutions.
    final int solutionLimit = 5;
    class VarArraySolutionPrinterWithLimit extends CpSolverSolutionCallback {
      public VarArraySolutionPrinterWithLimit(
          int[] allNurses, int[] allDays, int[] allShifts, Literal[][][] shifts, int limit) {
        solutionCount = 0;
        this.allNurses = allNurses;
        this.allDays = allDays;
        this.allShifts = allShifts;
        this.shifts = shifts;
        solutionLimit = limit;
      }

      @Override
      public void onSolutionCallback() {
        System.out.printf("Solution #%d:%n", solutionCount);
        for (int d : allDays) {
          System.out.printf("Day %d%n", d);
          for (int n : allNurses) {
            boolean isWorking = false;
            for (int s : allShifts) {
              if (booleanValue(shifts[n][d][s])) {
                isWorking = true;
                System.out.printf("  Nurse %d work shift %d%n", n, s);
              }
            }
            if (!isWorking) {
              System.out.printf("  Nurse %d does not work%n", n);
            }
          }
        }
        solutionCount++;
        if (solutionCount >= solutionLimit) {
          System.out.printf("Stop search after %d solutions%n", solutionLimit);
          stopSearch();
        }
      }

      public int getSolutionCount() {
        return solutionCount;
      }

      private int solutionCount;
      private final int[] allNurses;
      private final int[] allDays;
      private final int[] allShifts;
      private final Literal[][][] shifts;
      private final int solutionLimit;
    }

    VarArraySolutionPrinterWithLimit cb =
        new VarArraySolutionPrinterWithLimit(allNurses, allDays, allShifts, shifts, solutionLimit);

    // Creates a solver and solves the model.
    CpSolverStatus status = solver.solve(model, cb);
    System.out.println("Status: " + status);
    System.out.println(cb.getSolutionCount() + " solutions found.");

    // Statistics.
    System.out.println("Statistics");
    System.out.printf("  conflicts: %d%n", solver.numConflicts());
    System.out.printf("  branches : %d%n", solver.numBranches());
    System.out.printf("  wall time: %f s%n", solver.wallTime());
  }

  private NursesSat() {}
}

C#

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Google.OrTools.Sat;

public class NursesSat
{
    public class SolutionPrinter : CpSolverSolutionCallback
    {
        public SolutionPrinter(int[] allNurses, int[] allDays, int[] allShifts,
                               Dictionary<(int, int, int), BoolVar> shifts, int limit)
        {
            solutionCount_ = 0;
            allNurses_ = allNurses;
            allDays_ = allDays;
            allShifts_ = allShifts;
            shifts_ = shifts;
            solutionLimit_ = limit;
        }

        public override void OnSolutionCallback()
        {
            Console.WriteLine($"Solution #{solutionCount_}:");
            foreach (int d in allDays_)
            {
                Console.WriteLine($"Day {d}");
                foreach (int n in allNurses_)
                {
                    bool isWorking = false;
                    foreach (int s in allShifts_)
                    {
                        if (Value(shifts_[(n, d, s)]) == 1L)
                        {
                            isWorking = true;
                            Console.WriteLine($"  Nurse {n} work shift {s}");
                        }
                    }
                    if (!isWorking)
                    {
                        Console.WriteLine($"  Nurse {d} does not work");
                    }
                }
            }
            solutionCount_++;
            if (solutionCount_ >= solutionLimit_)
            {
                Console.WriteLine($"Stop search after {solutionLimit_} solutions");
                StopSearch();
            }
        }

        public int SolutionCount()
        {
            return solutionCount_;
        }

        private int solutionCount_;
        private int[] allNurses_;
        private int[] allDays_;
        private int[] allShifts_;
        private Dictionary<(int, int, int), BoolVar> shifts_;
        private int solutionLimit_;
    }

    public static void Main(String[] args)
    {
        const int numNurses = 4;
        const int numDays = 3;
        const int numShifts = 3;

        int[] allNurses = Enumerable.Range(0, numNurses).ToArray();
        int[] allDays = Enumerable.Range(0, numDays).ToArray();
        int[] allShifts = Enumerable.Range(0, numShifts).ToArray();

        // Creates the model.
        CpModel model = new CpModel();
        model.Model.Variables.Capacity = numNurses * numDays * numShifts;

        // Creates shift variables.
        // shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
        Dictionary<(int, int, int), BoolVar> shifts =
            new Dictionary<(int, int, int), BoolVar>(numNurses * numDays * numShifts);
        foreach (int n in allNurses)
        {
            foreach (int d in allDays)
            {
                foreach (int s in allShifts)
                {
                    shifts.Add((n, d, s), model.NewBoolVar($"shifts_n{n}d{d}s{s}"));
                }
            }
        }

        // Each shift is assigned to exactly one nurse in the schedule period.
        List<ILiteral> literals = new List<ILiteral>();
        foreach (int d in allDays)
        {
            foreach (int s in allShifts)
            {
                foreach (int n in allNurses)
                {
                    literals.Add(shifts[(n, d, s)]);
                }
                model.AddExactlyOne(literals);
                literals.Clear();
            }
        }

        // Each nurse works at most one shift per day.
        foreach (int n in allNurses)
        {
            foreach (int d in allDays)
            {
                foreach (int s in allShifts)
                {
                    literals.Add(shifts[(n, d, s)]);
                }
                model.AddAtMostOne(literals);
                literals.Clear();
            }
        }

        // Try to distribute the shifts evenly, so that each nurse works
        // minShiftsPerNurse shifts. If this is not possible, because the total
        // number of shifts is not divisible by the number of nurses, some nurses will
        // be assigned one more shift.
        int minShiftsPerNurse = (numShifts * numDays) / numNurses;
        int maxShiftsPerNurse;
        if ((numShifts * numDays) % numNurses == 0)
        {
            maxShiftsPerNurse = minShiftsPerNurse;
        }
        else
        {
            maxShiftsPerNurse = minShiftsPerNurse + 1;
        }

        List<IntVar> shiftsWorked = new List<IntVar>();
        foreach (int n in allNurses)
        {
            foreach (int d in allDays)
            {
                foreach (int s in allShifts)
                {
                    shiftsWorked.Add(shifts[(n, d, s)]);
                }
            }
            model.AddLinearConstraint(LinearExpr.Sum(shiftsWorked), minShiftsPerNurse, maxShiftsPerNurse);
            shiftsWorked.Clear();
        }

        CpSolver solver = new CpSolver();
        // Tell the solver to enumerate all solutions.
        solver.StringParameters += "linearization_level:0 " + "enumerate_all_solutions:true ";

        // Display the first five solutions.
        const int solutionLimit = 5;
        SolutionPrinter cb = new SolutionPrinter(allNurses, allDays, allShifts, shifts, solutionLimit);

        // Solve
        CpSolverStatus status = solver.Solve(model, cb);
        Console.WriteLine($"Solve status: {status}");

        Console.WriteLine("Statistics");
        Console.WriteLine($"  conflicts: {solver.NumConflicts()}");
        Console.WriteLine($"  branches : {solver.NumBranches()}");
        Console.WriteLine($"  wall time: {solver.WallTime()}s");
    }
}

शिफ़्ट के अनुरोध के साथ शेड्यूल करना

इस सेक्शन में, हम पिछला उदाहरण लेते हैं. इसके बाद, खास बदलावों के बारे में बताया है. इसके बाद, हम ऐसा शेड्यूल ढूंढेंगे जिसमें पूरा होने वाले अनुरोधों की संख्या ज़्यादा से ज़्यादा हो. शेड्यूल करने से जुड़ी ज़्यादातर समस्याओं के लिए, मकसद फ़ंक्शन को ऑप्टिमाइज़ करना सबसे अच्छा होता है, क्योंकि किया जाता है, तो सभी संभावित शेड्यूल प्रिंट नहीं किए जा सकते.

इस उदाहरण में वही पाबंदियां हैं जो पिछले उदाहरण में दी गई हैं.

लाइब्रेरी इंपोर्ट करें

यहां दिया गया कोड ज़रूरी लाइब्रेरी इंपोर्ट करता है.

Python

from typing import Union

from ortools.sat.python import cp_model

C++

#include <stdlib.h>

#include <cstdint>
#include <map>
#include <numeric>
#include <string>
#include <tuple>
#include <vector>

#include "absl/strings/str_format.h"
#include "ortools/base/logging.h"
#include "ortools/sat/cp_model.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/sat/cp_model_solver.h"

Java

import com.google.ortools.Loader;
import com.google.ortools.sat.CpModel;
import com.google.ortools.sat.CpSolver;
import com.google.ortools.sat.CpSolverStatus;
import com.google.ortools.sat.LinearExpr;
import com.google.ortools.sat.LinearExprBuilder;
import com.google.ortools.sat.Literal;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

C#

using System;
using System.Collections.Generic;
using System.Linq;
using Google.OrTools.Sat;

उदाहरण के लिए डेटा

इस उदाहरण का डेटा इसके बाद दिखाया गया है.

Python

num_nurses = 5
num_shifts = 3
num_days = 7
all_nurses = range(num_nurses)
all_shifts = range(num_shifts)
all_days = range(num_days)
shift_requests = [
    [[0, 0, 1], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 0, 1]],
    [[0, 0, 0], [0, 0, 0], [0, 1, 0], [0, 1, 0], [1, 0, 0], [0, 0, 0], [0, 0, 1]],
    [[0, 1, 0], [0, 1, 0], [0, 0, 0], [1, 0, 0], [0, 0, 0], [0, 1, 0], [0, 0, 0]],
    [[0, 0, 1], [0, 0, 0], [1, 0, 0], [0, 1, 0], [0, 0, 0], [1, 0, 0], [0, 0, 0]],
    [[0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 0, 0], [1, 0, 0], [0, 1, 0], [0, 0, 0]],
]

C++

const int num_nurses = 5;
const int num_days = 7;
const int num_shifts = 3;

std::vector<int> all_nurses(num_nurses);
std::iota(all_nurses.begin(), all_nurses.end(), 0);

std::vector<int> all_days(num_days);
std::iota(all_days.begin(), all_days.end(), 0);

std::vector<int> all_shifts(num_shifts);
std::iota(all_shifts.begin(), all_shifts.end(), 0);

std::vector<std::vector<std::vector<int64_t>>> shift_requests = {
    {
        {0, 0, 1},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 1},
        {0, 1, 0},
        {0, 0, 1},
    },
    {
        {0, 0, 0},
        {0, 0, 0},
        {0, 1, 0},
        {0, 1, 0},
        {1, 0, 0},
        {0, 0, 0},
        {0, 0, 1},
    },
    {
        {0, 1, 0},
        {0, 1, 0},
        {0, 0, 0},
        {1, 0, 0},
        {0, 0, 0},
        {0, 1, 0},
        {0, 0, 0},
    },
    {
        {0, 0, 1},
        {0, 0, 0},
        {1, 0, 0},
        {0, 1, 0},
        {0, 0, 0},
        {1, 0, 0},
        {0, 0, 0},
    },
    {
        {0, 0, 0},
        {0, 0, 1},
        {0, 1, 0},
        {0, 0, 0},
        {1, 0, 0},
        {0, 1, 0},
        {0, 0, 0},
    },
};

Java

final int numNurses = 5;
final int numDays = 7;
final int numShifts = 3;

final int[] allNurses = IntStream.range(0, numNurses).toArray();
final int[] allDays = IntStream.range(0, numDays).toArray();
final int[] allShifts = IntStream.range(0, numShifts).toArray();

final int[][][] shiftRequests = new int[][][] {
    {
        {0, 0, 1},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 0},
        {0, 0, 1},
        {0, 1, 0},
        {0, 0, 1},
    },
    {
        {0, 0, 0},
        {0, 0, 0},
        {0, 1, 0},
        {0, 1, 0},
        {1, 0, 0},
        {0, 0, 0},
        {0, 0, 1},
    },
    {
        {0, 1, 0},
        {0, 1, 0},
        {0, 0, 0},
        {1, 0, 0},
        {0, 0, 0},
        {0, 1, 0},
        {0, 0, 0},
    },
    {
        {0, 0, 1},
        {0, 0, 0},
        {1, 0, 0},
        {0, 1, 0},
        {0, 0, 0},
        {1, 0, 0},
        {0, 0, 0},
    },
    {
        {0, 0, 0},
        {0, 0, 1},
        {0, 1, 0},
        {0, 0, 0},
        {1, 0, 0},
        {0, 1, 0},
        {0, 0, 0},
    },
};

C#

const int numNurses = 5;
const int numDays = 7;
const int numShifts = 3;

int[] allNurses = Enumerable.Range(0, numNurses).ToArray();
int[] allDays = Enumerable.Range(0, numDays).ToArray();
int[] allShifts = Enumerable.Range(0, numShifts).ToArray();

int[,,] shiftRequests = new int[,,] {
    {
        { 0, 0, 1 },
        { 0, 0, 0 },
        { 0, 0, 0 },
        { 0, 0, 0 },
        { 0, 0, 1 },
        { 0, 1, 0 },
        { 0, 0, 1 },
    },
    {
        { 0, 0, 0 },
        { 0, 0, 0 },
        { 0, 1, 0 },
        { 0, 1, 0 },
        { 1, 0, 0 },
        { 0, 0, 0 },
        { 0, 0, 1 },
    },
    {
        { 0, 1, 0 },
        { 0, 1, 0 },
        { 0, 0, 0 },
        { 1, 0, 0 },
        { 0, 0, 0 },
        { 0, 1, 0 },
        { 0, 0, 0 },
    },
    {
        { 0, 0, 1 },
        { 0, 0, 0 },
        { 1, 0, 0 },
        { 0, 1, 0 },
        { 0, 0, 0 },
        { 1, 0, 0 },
        { 0, 0, 0 },
    },
    {
        { 0, 0, 0 },
        { 0, 0, 1 },
        { 0, 1, 0 },
        { 0, 0, 0 },
        { 1, 0, 0 },
        { 0, 1, 0 },
        { 0, 0, 0 },
    },
};

मॉडल बनाना

यह कोड मॉडल बनाता है.

Python

model = cp_model.CpModel()

C++

CpModelBuilder cp_model;

Java

CpModel model = new CpModel();

C#

CpModel model = new CpModel();

वैरिएबल बनाना

समस्या के लिए वैरिएबल की एक अरे यहां कोड में डाली गई है.

पिछले उदाहरण में दिए गए वैरिएबल के अलावा, डेटा में इसमें तीन बार का बदलाव दिख सकता है. यह हर दिन तीन शिफ़्ट में होने वाला है. इसका हर एक एलिमेंट तीन की वैल्यू 0 होती है या 1. इससे पता चलता है कि शिफ़्ट का अनुरोध किया गया था या नहीं. उदाहरण के लिए, पंक्ति 1 की पांचवीं स्थिति में तीन [0, 0, 1] का मतलब है कि नर्स 1 अनुरोध करती है दिन 5 पर 3 शिफ़्ट हो गया है.

Python

shifts = {}
for n in all_nurses:
    for d in all_days:
        for s in all_shifts:
            shifts[(n, d, s)] = model.new_bool_var(f"shift_n{n}_d{d}_s{s}")

C++

std::map<std::tuple<int, int, int>, BoolVar> shifts;
for (int n : all_nurses) {
  for (int d : all_days) {
    for (int s : all_shifts) {
      auto key = std::make_tuple(n, d, s);
      shifts[key] = cp_model.NewBoolVar().WithName(
          absl::StrFormat("shift_n%dd%ds%d", n, d, s));
    }
  }
}

Java

Literal[][][] shifts = new Literal[numNurses][numDays][numShifts];
for (int n : allNurses) {
  for (int d : allDays) {
    for (int s : allShifts) {
      shifts[n][d][s] = model.newBoolVar("shifts_n" + n + "d" + d + "s" + s);
    }
  }
}

C#

Dictionary<Tuple<int, int, int>, IntVar> shifts = new Dictionary<Tuple<int, int, int>, IntVar>();
foreach (int n in allNurses)
{
    foreach (int d in allDays)
    {
        foreach (int s in allShifts)
        {
            shifts.Add(Tuple.Create(n, d, s), model.NewBoolVar($"shifts_n{n}d{d}s{s}"));
        }
    }
}

कंस्ट्रेंट बनाएं

नीचे दिया गया कोड समस्या की वजह से सीमाएं बनाता है.

Python

for d in all_days:
    for s in all_shifts:
        model.add_exactly_one(shifts[(n, d, s)] for n in all_nurses)

C++

for (int d : all_days) {
  for (int s : all_shifts) {
    std::vector<BoolVar> nurses;
    for (int n : all_nurses) {
      auto key = std::make_tuple(n, d, s);
      nurses.push_back(shifts[key]);
    }
    cp_model.AddExactlyOne(nurses);
  }
}

Java

for (int d : allDays) {
  for (int s : allShifts) {
    List<Literal> nurses = new ArrayList<>();
    for (int n : allNurses) {
      nurses.add(shifts[n][d][s]);
    }
    model.addExactlyOne(nurses);
  }
}

C#

foreach (int d in allDays)
{
    foreach (int s in allShifts)
    {
        IntVar[] x = new IntVar[numNurses];
        foreach (int n in allNurses)
        {
            var key = Tuple.Create(n, d, s);
            x[n] = shifts[key];
        }
        model.Add(LinearExpr.Sum(x) == 1);
    }
}

Python

for n in all_nurses:
    for d in all_days:
        model.add_at_most_one(shifts[(n, d, s)] for s in all_shifts)

C++

for (int n : all_nurses) {
  for (int d : all_days) {
    std::vector<BoolVar> work;
    for (int s : all_shifts) {
      auto key = std::make_tuple(n, d, s);
      work.push_back(shifts[key]);
    }
    cp_model.AddAtMostOne(work);
  }
}

Java

for (int n : allNurses) {
  for (int d : allDays) {
    List<Literal> work = new ArrayList<>();
    for (int s : allShifts) {
      work.add(shifts[n][d][s]);
    }
    model.addAtMostOne(work);
  }
}

C#

foreach (int n in allNurses)
{
    foreach (int d in allDays)
    {
        IntVar[] x = new IntVar[numShifts];
        foreach (int s in allShifts)
        {
            var key = Tuple.Create(n, d, s);
            x[s] = shifts[key];
        }
        model.Add(LinearExpr.Sum(x) <= 1);
    }
}

Python

# Try to distribute the shifts evenly, so that each nurse works
# min_shifts_per_nurse shifts. If this is not possible, because the total
# number of shifts is not divisible by the number of nurses, some nurses will
# be assigned one more shift.
min_shifts_per_nurse = (num_shifts * num_days) // num_nurses
if num_shifts * num_days % num_nurses == 0:
    max_shifts_per_nurse = min_shifts_per_nurse
else:
    max_shifts_per_nurse = min_shifts_per_nurse + 1
for n in all_nurses:
    num_shifts_worked: Union[cp_model.LinearExpr, int] = 0
    for d in all_days:
        for s in all_shifts:
            num_shifts_worked += shifts[(n, d, s)]
    model.add(min_shifts_per_nurse <= num_shifts_worked)
    model.add(num_shifts_worked <= max_shifts_per_nurse)

C++

// Try to distribute the shifts evenly, so that each nurse works
// min_shifts_per_nurse shifts. If this is not possible, because the total
// number of shifts is not divisible by the number of nurses, some nurses will
// be assigned one more shift.
int min_shifts_per_nurse = (num_shifts * num_days) / num_nurses;
int max_shifts_per_nurse;
if ((num_shifts * num_days) % num_nurses == 0) {
  max_shifts_per_nurse = min_shifts_per_nurse;
} else {
  max_shifts_per_nurse = min_shifts_per_nurse + 1;
}
for (int n : all_nurses) {
  LinearExpr num_worked_shifts;
  for (int d : all_days) {
    for (int s : all_shifts) {
      auto key = std::make_tuple(n, d, s);
      num_worked_shifts += shifts[key];
    }
  }
  cp_model.AddLessOrEqual(min_shifts_per_nurse, num_worked_shifts);
  cp_model.AddLessOrEqual(num_worked_shifts, max_shifts_per_nurse);
}

Java

// Try to distribute the shifts evenly, so that each nurse works
// minShiftsPerNurse shifts. If this is not possible, because the total
// number of shifts is not divisible by the number of nurses, some nurses will
// be assigned one more shift.
int minShiftsPerNurse = (numShifts * numDays) / numNurses;
int maxShiftsPerNurse;
if ((numShifts * numDays) % numNurses == 0) {
  maxShiftsPerNurse = minShiftsPerNurse;
} else {
  maxShiftsPerNurse = minShiftsPerNurse + 1;
}
for (int n : allNurses) {
  LinearExprBuilder numShiftsWorked = LinearExpr.newBuilder();
  for (int d : allDays) {
    for (int s : allShifts) {
      numShiftsWorked.add(shifts[n][d][s]);
    }
  }
  model.addLinearConstraint(numShiftsWorked, minShiftsPerNurse, maxShiftsPerNurse);
}

C#

// Try to distribute the shifts evenly, so that each nurse works
// minShiftsPerNurse shifts. If this is not possible, because the total
// number of shifts is not divisible by the number of nurses, some nurses will
// be assigned one more shift.
int minShiftsPerNurse = (numShifts * numDays) / numNurses;
int maxShiftsPerNurse;
if ((numShifts * numDays) % numNurses == 0)
{
    maxShiftsPerNurse = minShiftsPerNurse;
}
else
{
    maxShiftsPerNurse = minShiftsPerNurse + 1;
}
foreach (int n in allNurses)
{
    IntVar[] numShiftsWorked = new IntVar[numDays * numShifts];
    foreach (int d in allDays)
    {
        foreach (int s in allShifts)
        {
            var key = Tuple.Create(n, d, s);
            numShiftsWorked[d * numShifts + s] = shifts[key];
        }
    }
    model.AddLinearConstraint(LinearExpr.Sum(numShiftsWorked), minShiftsPerNurse, maxShiftsPerNurse);
}

उदाहरण का मकसद

हम नीचे दिए गए मकसद फ़ंक्शन को ऑप्टिमाइज़ करना चाहते हैं.

Python

model.maximize(
    sum(
        shift_requests[n][d][s] * shifts[(n, d, s)]
        for n in all_nurses
        for d in all_days
        for s in all_shifts
    )
)

C++

LinearExpr objective_expr;
for (int n : all_nurses) {
  for (int d : all_days) {
    for (int s : all_shifts) {
      if (shift_requests[n][d][s] == 1) {
        auto key = std::make_tuple(n, d, s);
        objective_expr += shifts[key] * shift_requests[n][d][s];
      }
    }
  }
}
cp_model.Maximize(objective_expr);

Java

LinearExprBuilder obj = LinearExpr.newBuilder();
for (int n : allNurses) {
  for (int d : allDays) {
    for (int s : allShifts) {
      obj.addTerm(shifts[n][d][s], shiftRequests[n][d][s]);
    }
  }
}
model.maximize(obj);

C#

IntVar[] flatShifts = new IntVar[numNurses * numDays * numShifts];
int[] flatShiftRequests = new int[numNurses * numDays * numShifts];
foreach (int n in allNurses)
{
    foreach (int d in allDays)
    {
        foreach (int s in allShifts)
        {
            var key = Tuple.Create(n, d, s);
            flatShifts[n * numDays * numShifts + d * numShifts + s] = shifts[key];
            flatShiftRequests[n * numDays * numShifts + d * numShifts + s] = shiftRequests[n, d, s];
        }
    }
}
model.Maximize(LinearExpr.WeightedSum(flatShifts, flatShiftRequests));

अगर शिफ़्ट s असाइन किया गया है, तो shift_requests[n][d][s] * shifts[(n, d, s) की वैल्यू 1 है n को d दिन को नर्स करेंगे और उस नर्स ने उस शिफ़्ट का अनुरोध किया है (और 0 नहीं है), इसका मकसद, अनुरोध को पूरा करने वाले असाइनमेंट में होने वाले बदलावों की संख्या है.

सॉल्वर आज़माएं

यहां दिया गया कोड, सॉल्वर को कॉल करता है.

Python

solver = cp_model.CpSolver()
status = solver.solve(model)

C++

const CpSolverResponse response = Solve(cp_model.Build());

Java

CpSolver solver = new CpSolver();
CpSolverStatus status = solver.solve(model);

C#

CpSolver solver = new CpSolver();
CpSolverStatus status = solver.Solve(model);
Console.WriteLine($"Solve status: {status}");

नतीजे दिखाएं

यह कोड यह आउटपुट दिखाता है, जिसमें सबसे बेहतर शेड्यूल (हालांकि, सिर्फ़ एक ही नहीं). आउटपुट से पता चलता है कि कौनसा असाइनमेंट के लिए किए गए अनुरोधों की संख्या और उन अनुरोधों की संख्या जो पूरे किए गए.

Python

if status == cp_model.OPTIMAL:
    print("Solution:")
    for d in all_days:
        print("Day", d)
        for n in all_nurses:
            for s in all_shifts:
                if solver.value(shifts[(n, d, s)]) == 1:
                    if shift_requests[n][d][s] == 1:
                        print("Nurse", n, "works shift", s, "(requested).")
                    else:
                        print("Nurse", n, "works shift", s, "(not requested).")
        print()
    print(
        f"Number of shift requests met = {solver.objective_value}",
        f"(out of {num_nurses * min_shifts_per_nurse})",
    )
else:
    print("No optimal solution found !")

C++

if (response.status() == CpSolverStatus::OPTIMAL) {
  LOG(INFO) << "Solution:";
  for (int d : all_days) {
    LOG(INFO) << "Day " << std::to_string(d);
    for (int n : all_nurses) {
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        if (SolutionIntegerValue(response, shifts[key]) == 1) {
          if (shift_requests[n][d][s] == 1) {
            LOG(INFO) << "  Nurse " << std::to_string(n) << " works shift "
                      << std::to_string(s) << " (requested).";
          } else {
            LOG(INFO) << "  Nurse " << std::to_string(n) << " works shift "
                      << std::to_string(s) << " (not requested).";
          }
        }
      }
    }
    LOG(INFO) << "";
  }
  LOG(INFO) << "Number of shift requests met = " << response.objective_value()
            << " (out of " << num_nurses * min_shifts_per_nurse << ")";
} else {
  LOG(INFO) << "No optimal solution found !";
}

Java

if (status == CpSolverStatus.OPTIMAL || status == CpSolverStatus.FEASIBLE) {
  System.out.printf("Solution:%n");
  for (int d : allDays) {
    System.out.printf("Day %d%n", d);
    for (int n : allNurses) {
      for (int s : allShifts) {
        if (solver.booleanValue(shifts[n][d][s])) {
          if (shiftRequests[n][d][s] == 1) {
            System.out.printf("  Nurse %d works shift %d (requested).%n", n, s);
          } else {
            System.out.printf("  Nurse %d works shift %d (not requested).%n", n, s);
          }
        }
      }
    }
  }
  System.out.printf("Number of shift requests met = %f (out of %d)%n", solver.objectiveValue(),
      numNurses * minShiftsPerNurse);
} else {
  System.out.printf("No optimal solution found !");
}

C#

if (status == CpSolverStatus.Optimal || status == CpSolverStatus.Feasible)
{
    Console.WriteLine("Solution:");
    foreach (int d in allDays)
    {
        Console.WriteLine($"Day {d}");
        foreach (int n in allNurses)
        {
            bool isWorking = false;
            foreach (int s in allShifts)
            {
                var key = Tuple.Create(n, d, s);
                if (solver.Value(shifts[key]) == 1L)
                {
                    if (shiftRequests[n, d, s] == 1)
                    {
                        Console.WriteLine($"  Nurse {n} work shift {s} (requested).");
                    }
                    else
                    {
                        Console.WriteLine($"  Nurse {n} work shift {s} (not requested).");
                    }
                }
            }
        }
    }
    Console.WriteLine(
        $"Number of shift requests met = {solver.ObjectiveValue} (out of {numNurses * minShiftsPerNurse}).");
}
else
{
    Console.WriteLine("No solution found.");
}

प्रोग्राम को चलाने पर, यह नीचे दिया गया आउटपुट दिखाता है:

Day 0
Nurse 1 works shift 0 (not requested).
Nurse 2 works shift 1 (requested).
Nurse 3 works shift 2 (requested).

Day 1
Nurse 0 works shift 0 (not requested).
Nurse 2 works shift 1 (requested).
Nurse 4 works shift 2 (requested).

Day 2
Nurse 1 works shift 2 (not requested).
Nurse 3 works shift 0 (requested).
Nurse 4 works shift 1 (requested).

Day 3
Nurse 2 works shift 0 (requested).
Nurse 3 works shift 1 (requested).
Nurse 4 works shift 2 (not requested).

Day 4
Nurse 0 works shift 2 (requested).
Nurse 1 works shift 0 (requested).
Nurse 4 works shift 1 (not requested).

Day 5
Nurse 0 works shift 2 (not requested).
Nurse 2 works shift 1 (requested).
Nurse 3 works shift 0 (requested).

Day 6
Nurse 0 works shift 1 (not requested).
Nurse 1 works shift 2 (requested).
Nurse 4 works shift 0 (not requested).

Statistics
  - Number of shift requests met = 13 (out of 20 )
  - wall time       : 0.003571 s

पूरा प्रोग्राम

शिफ़्ट के अनुरोधों के साथ शेड्यूल करने के लिए पूरा प्रोग्राम यहां दिया गया है.

Python

"""Nurse scheduling problem with shift requests."""
from typing import Union

from ortools.sat.python import cp_model


def main() -> None:
    # This program tries to find an optimal assignment of nurses to shifts
    # (3 shifts per day, for 7 days), subject to some constraints (see below).
    # Each nurse can request to be assigned to specific shifts.
    # The optimal assignment maximizes the number of fulfilled shift requests.
    num_nurses = 5
    num_shifts = 3
    num_days = 7
    all_nurses = range(num_nurses)
    all_shifts = range(num_shifts)
    all_days = range(num_days)
    shift_requests = [
        [[0, 0, 1], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 0, 1]],
        [[0, 0, 0], [0, 0, 0], [0, 1, 0], [0, 1, 0], [1, 0, 0], [0, 0, 0], [0, 0, 1]],
        [[0, 1, 0], [0, 1, 0], [0, 0, 0], [1, 0, 0], [0, 0, 0], [0, 1, 0], [0, 0, 0]],
        [[0, 0, 1], [0, 0, 0], [1, 0, 0], [0, 1, 0], [0, 0, 0], [1, 0, 0], [0, 0, 0]],
        [[0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 0, 0], [1, 0, 0], [0, 1, 0], [0, 0, 0]],
    ]

    # Creates the model.
    model = cp_model.CpModel()

    # Creates shift variables.
    # shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
    shifts = {}
    for n in all_nurses:
        for d in all_days:
            for s in all_shifts:
                shifts[(n, d, s)] = model.new_bool_var(f"shift_n{n}_d{d}_s{s}")

    # Each shift is assigned to exactly one nurse in .
    for d in all_days:
        for s in all_shifts:
            model.add_exactly_one(shifts[(n, d, s)] for n in all_nurses)

    # Each nurse works at most one shift per day.
    for n in all_nurses:
        for d in all_days:
            model.add_at_most_one(shifts[(n, d, s)] for s in all_shifts)

    # Try to distribute the shifts evenly, so that each nurse works
    # min_shifts_per_nurse shifts. If this is not possible, because the total
    # number of shifts is not divisible by the number of nurses, some nurses will
    # be assigned one more shift.
    min_shifts_per_nurse = (num_shifts * num_days) // num_nurses
    if num_shifts * num_days % num_nurses == 0:
        max_shifts_per_nurse = min_shifts_per_nurse
    else:
        max_shifts_per_nurse = min_shifts_per_nurse + 1
    for n in all_nurses:
        num_shifts_worked: Union[cp_model.LinearExpr, int] = 0
        for d in all_days:
            for s in all_shifts:
                num_shifts_worked += shifts[(n, d, s)]
        model.add(min_shifts_per_nurse <= num_shifts_worked)
        model.add(num_shifts_worked <= max_shifts_per_nurse)

    model.maximize(
        sum(
            shift_requests[n][d][s] * shifts[(n, d, s)]
            for n in all_nurses
            for d in all_days
            for s in all_shifts
        )
    )

    # Creates the solver and solve.
    solver = cp_model.CpSolver()
    status = solver.solve(model)

    if status == cp_model.OPTIMAL:
        print("Solution:")
        for d in all_days:
            print("Day", d)
            for n in all_nurses:
                for s in all_shifts:
                    if solver.value(shifts[(n, d, s)]) == 1:
                        if shift_requests[n][d][s] == 1:
                            print("Nurse", n, "works shift", s, "(requested).")
                        else:
                            print("Nurse", n, "works shift", s, "(not requested).")
            print()
        print(
            f"Number of shift requests met = {solver.objective_value}",
            f"(out of {num_nurses * min_shifts_per_nurse})",
        )
    else:
        print("No optimal solution found !")

    # Statistics.
    print("\nStatistics")
    print(f"  - conflicts: {solver.num_conflicts}")
    print(f"  - branches : {solver.num_branches}")
    print(f"  - wall time: {solver.wall_time}s")


if __name__ == "__main__":
    main()

C++

// Nurse scheduling problem with shift requests.
#include <stdlib.h>

#include <cstdint>
#include <map>
#include <numeric>
#include <string>
#include <tuple>
#include <vector>

#include "absl/strings/str_format.h"
#include "ortools/base/logging.h"
#include "ortools/sat/cp_model.h"
#include "ortools/sat/cp_model.pb.h"
#include "ortools/sat/cp_model_solver.h"

namespace operations_research {
namespace sat {

void ScheduleRequestsSat() {
  const int num_nurses = 5;
  const int num_days = 7;
  const int num_shifts = 3;

  std::vector<int> all_nurses(num_nurses);
  std::iota(all_nurses.begin(), all_nurses.end(), 0);

  std::vector<int> all_days(num_days);
  std::iota(all_days.begin(), all_days.end(), 0);

  std::vector<int> all_shifts(num_shifts);
  std::iota(all_shifts.begin(), all_shifts.end(), 0);

  std::vector<std::vector<std::vector<int64_t>>> shift_requests = {
      {
          {0, 0, 1},
          {0, 0, 0},
          {0, 0, 0},
          {0, 0, 0},
          {0, 0, 1},
          {0, 1, 0},
          {0, 0, 1},
      },
      {
          {0, 0, 0},
          {0, 0, 0},
          {0, 1, 0},
          {0, 1, 0},
          {1, 0, 0},
          {0, 0, 0},
          {0, 0, 1},
      },
      {
          {0, 1, 0},
          {0, 1, 0},
          {0, 0, 0},
          {1, 0, 0},
          {0, 0, 0},
          {0, 1, 0},
          {0, 0, 0},
      },
      {
          {0, 0, 1},
          {0, 0, 0},
          {1, 0, 0},
          {0, 1, 0},
          {0, 0, 0},
          {1, 0, 0},
          {0, 0, 0},
      },
      {
          {0, 0, 0},
          {0, 0, 1},
          {0, 1, 0},
          {0, 0, 0},
          {1, 0, 0},
          {0, 1, 0},
          {0, 0, 0},
      },
  };

  // Creates the model.
  CpModelBuilder cp_model;

  // Creates shift variables.
  // shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
  std::map<std::tuple<int, int, int>, BoolVar> shifts;
  for (int n : all_nurses) {
    for (int d : all_days) {
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        shifts[key] = cp_model.NewBoolVar().WithName(
            absl::StrFormat("shift_n%dd%ds%d", n, d, s));
      }
    }
  }

  // Each shift is assigned to exactly one nurse in the schedule period.
  for (int d : all_days) {
    for (int s : all_shifts) {
      std::vector<BoolVar> nurses;
      for (int n : all_nurses) {
        auto key = std::make_tuple(n, d, s);
        nurses.push_back(shifts[key]);
      }
      cp_model.AddExactlyOne(nurses);
    }
  }

  // Each nurse works at most one shift per day.
  for (int n : all_nurses) {
    for (int d : all_days) {
      std::vector<BoolVar> work;
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        work.push_back(shifts[key]);
      }
      cp_model.AddAtMostOne(work);
    }
  }

  // Try to distribute the shifts evenly, so that each nurse works
  // min_shifts_per_nurse shifts. If this is not possible, because the total
  // number of shifts is not divisible by the number of nurses, some nurses will
  // be assigned one more shift.
  int min_shifts_per_nurse = (num_shifts * num_days) / num_nurses;
  int max_shifts_per_nurse;
  if ((num_shifts * num_days) % num_nurses == 0) {
    max_shifts_per_nurse = min_shifts_per_nurse;
  } else {
    max_shifts_per_nurse = min_shifts_per_nurse + 1;
  }
  for (int n : all_nurses) {
    LinearExpr num_worked_shifts;
    for (int d : all_days) {
      for (int s : all_shifts) {
        auto key = std::make_tuple(n, d, s);
        num_worked_shifts += shifts[key];
      }
    }
    cp_model.AddLessOrEqual(min_shifts_per_nurse, num_worked_shifts);
    cp_model.AddLessOrEqual(num_worked_shifts, max_shifts_per_nurse);
  }

  LinearExpr objective_expr;
  for (int n : all_nurses) {
    for (int d : all_days) {
      for (int s : all_shifts) {
        if (shift_requests[n][d][s] == 1) {
          auto key = std::make_tuple(n, d, s);
          objective_expr += shifts[key] * shift_requests[n][d][s];
        }
      }
    }
  }
  cp_model.Maximize(objective_expr);

  const CpSolverResponse response = Solve(cp_model.Build());

  if (response.status() == CpSolverStatus::OPTIMAL) {
    LOG(INFO) << "Solution:";
    for (int d : all_days) {
      LOG(INFO) << "Day " << std::to_string(d);
      for (int n : all_nurses) {
        for (int s : all_shifts) {
          auto key = std::make_tuple(n, d, s);
          if (SolutionIntegerValue(response, shifts[key]) == 1) {
            if (shift_requests[n][d][s] == 1) {
              LOG(INFO) << "  Nurse " << std::to_string(n) << " works shift "
                        << std::to_string(s) << " (requested).";
            } else {
              LOG(INFO) << "  Nurse " << std::to_string(n) << " works shift "
                        << std::to_string(s) << " (not requested).";
            }
          }
        }
      }
      LOG(INFO) << "";
    }
    LOG(INFO) << "Number of shift requests met = " << response.objective_value()
              << " (out of " << num_nurses * min_shifts_per_nurse << ")";
  } else {
    LOG(INFO) << "No optimal solution found !";
  }

  // Statistics.
  LOG(INFO) << "Statistics";
  LOG(INFO) << CpSolverResponseStats(response);
}

}  // namespace sat
}  // namespace operations_research

int main() {
  operations_research::sat::ScheduleRequestsSat();
  return EXIT_SUCCESS;
}

Java

package com.google.ortools.sat.samples;
import com.google.ortools.Loader;
import com.google.ortools.sat.CpModel;
import com.google.ortools.sat.CpSolver;
import com.google.ortools.sat.CpSolverStatus;
import com.google.ortools.sat.LinearExpr;
import com.google.ortools.sat.LinearExprBuilder;
import com.google.ortools.sat.Literal;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

/** Nurses problem with schedule requests. */
public class ScheduleRequestsSat {
  public static void main(String[] args) {
    Loader.loadNativeLibraries();
    final int numNurses = 5;
    final int numDays = 7;
    final int numShifts = 3;

    final int[] allNurses = IntStream.range(0, numNurses).toArray();
    final int[] allDays = IntStream.range(0, numDays).toArray();
    final int[] allShifts = IntStream.range(0, numShifts).toArray();

    final int[][][] shiftRequests = new int[][][] {
        {
            {0, 0, 1},
            {0, 0, 0},
            {0, 0, 0},
            {0, 0, 0},
            {0, 0, 1},
            {0, 1, 0},
            {0, 0, 1},
        },
        {
            {0, 0, 0},
            {0, 0, 0},
            {0, 1, 0},
            {0, 1, 0},
            {1, 0, 0},
            {0, 0, 0},
            {0, 0, 1},
        },
        {
            {0, 1, 0},
            {0, 1, 0},
            {0, 0, 0},
            {1, 0, 0},
            {0, 0, 0},
            {0, 1, 0},
            {0, 0, 0},
        },
        {
            {0, 0, 1},
            {0, 0, 0},
            {1, 0, 0},
            {0, 1, 0},
            {0, 0, 0},
            {1, 0, 0},
            {0, 0, 0},
        },
        {
            {0, 0, 0},
            {0, 0, 1},
            {0, 1, 0},
            {0, 0, 0},
            {1, 0, 0},
            {0, 1, 0},
            {0, 0, 0},
        },
    };

    // Creates the model.
    CpModel model = new CpModel();

    // Creates shift variables.
    // shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
    Literal[][][] shifts = new Literal[numNurses][numDays][numShifts];
    for (int n : allNurses) {
      for (int d : allDays) {
        for (int s : allShifts) {
          shifts[n][d][s] = model.newBoolVar("shifts_n" + n + "d" + d + "s" + s);
        }
      }
    }

    // Each shift is assigned to exactly one nurse in the schedule period.
    for (int d : allDays) {
      for (int s : allShifts) {
        List<Literal> nurses = new ArrayList<>();
        for (int n : allNurses) {
          nurses.add(shifts[n][d][s]);
        }
        model.addExactlyOne(nurses);
      }
    }

    // Each nurse works at most one shift per day.
    for (int n : allNurses) {
      for (int d : allDays) {
        List<Literal> work = new ArrayList<>();
        for (int s : allShifts) {
          work.add(shifts[n][d][s]);
        }
        model.addAtMostOne(work);
      }
    }

    // Try to distribute the shifts evenly, so that each nurse works
    // minShiftsPerNurse shifts. If this is not possible, because the total
    // number of shifts is not divisible by the number of nurses, some nurses will
    // be assigned one more shift.
    int minShiftsPerNurse = (numShifts * numDays) / numNurses;
    int maxShiftsPerNurse;
    if ((numShifts * numDays) % numNurses == 0) {
      maxShiftsPerNurse = minShiftsPerNurse;
    } else {
      maxShiftsPerNurse = minShiftsPerNurse + 1;
    }
    for (int n : allNurses) {
      LinearExprBuilder numShiftsWorked = LinearExpr.newBuilder();
      for (int d : allDays) {
        for (int s : allShifts) {
          numShiftsWorked.add(shifts[n][d][s]);
        }
      }
      model.addLinearConstraint(numShiftsWorked, minShiftsPerNurse, maxShiftsPerNurse);
    }

    LinearExprBuilder obj = LinearExpr.newBuilder();
    for (int n : allNurses) {
      for (int d : allDays) {
        for (int s : allShifts) {
          obj.addTerm(shifts[n][d][s], shiftRequests[n][d][s]);
        }
      }
    }
    model.maximize(obj);

    // Creates a solver and solves the model.
    CpSolver solver = new CpSolver();
    CpSolverStatus status = solver.solve(model);

    if (status == CpSolverStatus.OPTIMAL || status == CpSolverStatus.FEASIBLE) {
      System.out.printf("Solution:%n");
      for (int d : allDays) {
        System.out.printf("Day %d%n", d);
        for (int n : allNurses) {
          for (int s : allShifts) {
            if (solver.booleanValue(shifts[n][d][s])) {
              if (shiftRequests[n][d][s] == 1) {
                System.out.printf("  Nurse %d works shift %d (requested).%n", n, s);
              } else {
                System.out.printf("  Nurse %d works shift %d (not requested).%n", n, s);
              }
            }
          }
        }
      }
      System.out.printf("Number of shift requests met = %f (out of %d)%n", solver.objectiveValue(),
          numNurses * minShiftsPerNurse);
    } else {
      System.out.printf("No optimal solution found !");
    }
    // Statistics.
    System.out.println("Statistics");
    System.out.printf("  conflicts: %d%n", solver.numConflicts());
    System.out.printf("  branches : %d%n", solver.numBranches());
    System.out.printf("  wall time: %f s%n", solver.wallTime());
  }

  private ScheduleRequestsSat() {}
}

C#

using System;
using System.Collections.Generic;
using System.Linq;
using Google.OrTools.Sat;

public class ScheduleRequestsSat
{
    public static void Main(String[] args)
    {
        const int numNurses = 5;
        const int numDays = 7;
        const int numShifts = 3;

        int[] allNurses = Enumerable.Range(0, numNurses).ToArray();
        int[] allDays = Enumerable.Range(0, numDays).ToArray();
        int[] allShifts = Enumerable.Range(0, numShifts).ToArray();

        int[,,] shiftRequests = new int[,,] {
            {
                { 0, 0, 1 },
                { 0, 0, 0 },
                { 0, 0, 0 },
                { 0, 0, 0 },
                { 0, 0, 1 },
                { 0, 1, 0 },
                { 0, 0, 1 },
            },
            {
                { 0, 0, 0 },
                { 0, 0, 0 },
                { 0, 1, 0 },
                { 0, 1, 0 },
                { 1, 0, 0 },
                { 0, 0, 0 },
                { 0, 0, 1 },
            },
            {
                { 0, 1, 0 },
                { 0, 1, 0 },
                { 0, 0, 0 },
                { 1, 0, 0 },
                { 0, 0, 0 },
                { 0, 1, 0 },
                { 0, 0, 0 },
            },
            {
                { 0, 0, 1 },
                { 0, 0, 0 },
                { 1, 0, 0 },
                { 0, 1, 0 },
                { 0, 0, 0 },
                { 1, 0, 0 },
                { 0, 0, 0 },
            },
            {
                { 0, 0, 0 },
                { 0, 0, 1 },
                { 0, 1, 0 },
                { 0, 0, 0 },
                { 1, 0, 0 },
                { 0, 1, 0 },
                { 0, 0, 0 },
            },
        };

        // Creates the model.
        CpModel model = new CpModel();

        // Creates shift variables.
        // shifts[(n, d, s)]: nurse 'n' works shift 's' on day 'd'.
        Dictionary<Tuple<int, int, int>, IntVar> shifts = new Dictionary<Tuple<int, int, int>, IntVar>();
        foreach (int n in allNurses)
        {
            foreach (int d in allDays)
            {
                foreach (int s in allShifts)
                {
                    shifts.Add(Tuple.Create(n, d, s), model.NewBoolVar($"shifts_n{n}d{d}s{s}"));
                }
            }
        }

        // Each shift is assigned to exactly one nurse in the schedule period.
        foreach (int d in allDays)
        {
            foreach (int s in allShifts)
            {
                IntVar[] x = new IntVar[numNurses];
                foreach (int n in allNurses)
                {
                    var key = Tuple.Create(n, d, s);
                    x[n] = shifts[key];
                }
                model.Add(LinearExpr.Sum(x) == 1);
            }
        }

        // Each nurse works at most one shift per day.
        foreach (int n in allNurses)
        {
            foreach (int d in allDays)
            {
                IntVar[] x = new IntVar[numShifts];
                foreach (int s in allShifts)
                {
                    var key = Tuple.Create(n, d, s);
                    x[s] = shifts[key];
                }
                model.Add(LinearExpr.Sum(x) <= 1);
            }
        }

        // Try to distribute the shifts evenly, so that each nurse works
        // minShiftsPerNurse shifts. If this is not possible, because the total
        // number of shifts is not divisible by the number of nurses, some nurses will
        // be assigned one more shift.
        int minShiftsPerNurse = (numShifts * numDays) / numNurses;
        int maxShiftsPerNurse;
        if ((numShifts * numDays) % numNurses == 0)
        {
            maxShiftsPerNurse = minShiftsPerNurse;
        }
        else
        {
            maxShiftsPerNurse = minShiftsPerNurse + 1;
        }
        foreach (int n in allNurses)
        {
            IntVar[] numShiftsWorked = new IntVar[numDays * numShifts];
            foreach (int d in allDays)
            {
                foreach (int s in allShifts)
                {
                    var key = Tuple.Create(n, d, s);
                    numShiftsWorked[d * numShifts + s] = shifts[key];
                }
            }
            model.AddLinearConstraint(LinearExpr.Sum(numShiftsWorked), minShiftsPerNurse, maxShiftsPerNurse);
        }

        IntVar[] flatShifts = new IntVar[numNurses * numDays * numShifts];
        int[] flatShiftRequests = new int[numNurses * numDays * numShifts];
        foreach (int n in allNurses)
        {
            foreach (int d in allDays)
            {
                foreach (int s in allShifts)
                {
                    var key = Tuple.Create(n, d, s);
                    flatShifts[n * numDays * numShifts + d * numShifts + s] = shifts[key];
                    flatShiftRequests[n * numDays * numShifts + d * numShifts + s] = shiftRequests[n, d, s];
                }
            }
        }
        model.Maximize(LinearExpr.WeightedSum(flatShifts, flatShiftRequests));

        // Solve
        CpSolver solver = new CpSolver();
        CpSolverStatus status = solver.Solve(model);
        Console.WriteLine($"Solve status: {status}");

        if (status == CpSolverStatus.Optimal || status == CpSolverStatus.Feasible)
        {
            Console.WriteLine("Solution:");
            foreach (int d in allDays)
            {
                Console.WriteLine($"Day {d}");
                foreach (int n in allNurses)
                {
                    bool isWorking = false;
                    foreach (int s in allShifts)
                    {
                        var key = Tuple.Create(n, d, s);
                        if (solver.Value(shifts[key]) == 1L)
                        {
                            if (shiftRequests[n, d, s] == 1)
                            {
                                Console.WriteLine($"  Nurse {n} work shift {s} (requested).");
                            }
                            else
                            {
                                Console.WriteLine($"  Nurse {n} work shift {s} (not requested).");
                            }
                        }
                    }
                }
            }
            Console.WriteLine(
                $"Number of shift requests met = {solver.ObjectiveValue} (out of {numNurses * minShiftsPerNurse}).");
        }
        else
        {
            Console.WriteLine("No solution found.");
        }

        Console.WriteLine("Statistics");
        Console.WriteLine($"  conflicts: {solver.NumConflicts()}");
        Console.WriteLine($"  branches : {solver.NumBranches()}");
        Console.WriteLine($"  wall time: {solver.WallTime()}s");
    }
}