为什么ILOG CP Optimizer出现seg故障

Question

我是约束编程的新手，正在尝试使用ILOG CP Optimizer将我的第一个问题建模为约束程序。我已经安装了ILOG Optimization Suite 20.1，并成功编译和运行了许多附带的示例文件。

我想做的是在两个单元上安排5项任务。每个任务都有一个发布时间和一个到期时间。此外，在每个单元上，每个任务都有处理时间和处理成本。

以下是我的代码。

#include <ilcp/cp.h>
#include <iostream>
using namespace std;
int main(int argc, const char * argv[]) 
{
IloEnv env;
try 
{
IloModel model(env);
IloInt numUnits = 2;
IloInt numTasks = 5;
IloIntervalVarArray dummyTasks(env, numTasks);
IloInt taskReleaseTimes[] = {0, 21, 15, 37, 3};
IloInt taskDueTimes[] = {200, 190, 172, 194, 161};
IloArray<IloBoolArray> unitTaskAssignment(env, numUnits);
unitTaskAssignment[0] = IloBoolArray(env, numTasks, IloTrue, IloTrue, IloFalse, IloTrue, IloTrue);
unitTaskAssignment[1] = IloBoolArray(env, numTasks, IloTrue, IloFalse, IloTrue, IloFalse, IloTrue);
IloArray<IloIntArray> unitTaskTimes(env, numUnits);
IloArray<IloNumArray> unitTaskCosts(env, numUnits);
IloIntArray minTaskTimes(env, numTasks);
IloIntArray maxTaskTimes(env, numTasks);
IloNumExpr totalCost(env);
unitTaskTimes[0] = IloIntArray(env, numTasks, 51, 67, 0, 24, 76);
unitTaskTimes[1] = IloIntArray(env, numTasks, 32, 0, 49, 0, 102);
unitTaskCosts[0] = IloNumArray(env, numTasks, 3.1, 3.7, 0.0, 3.4, 3.6);
unitTaskCosts[1] = IloNumArray(env, numTasks, 3.2, 0.0, 3.9, 0.0, 3.2);
IloArray<IloIntervalVarArray> taskUnits(env, numTasks);
IloArray<IloIntervalVarArray> unitTasks(env, numUnits);

for(IloInt i = 0; i < numTasks; i++)
{
IloInt minTaskTime = unitTaskTimes[0][i];
IloInt maxTaskTime = unitTaskTimes[0][i];
for(IloInt j = 1; j < numUnits; j++)
{
if(unitTaskTimes[j][i] < minTaskTime) minTaskTime = unitTaskTimes[j][i];
if(unitTaskTimes[j][i] > maxTaskTime) maxTaskTime = unitTaskTimes[j][i];
}
minTaskTimes[i] = minTaskTime;
maxTaskTimes[i] = maxTaskTime;
/*            cout << "Minimum task time for task " << i << ": " << minTaskTimes[i] << endl;*/
/*            cout << "Maximum task time for task " << i << ": " << maxTaskTimes[i] << endl;*/
}

char name[128];
for(IloInt i = 0; i < numTasks; i++)
{
taskUnits[i] = IloIntervalVarArray(env, numUnits);
sprintf(name, "dummyTask_%ld", i);
dummyTasks[i] = IloIntervalVar(env, minTaskTimes[i], maxTaskTimes[i]);
dummyTasks[i].setStartMin(taskReleaseTimes[i]);
dummyTasks[i].setEndMax(taskDueTimes[i]);
for(IloInt j = 0; j < numUnits; j++)
{
sprintf(name, "task%ld_in_unit%ld", j, i);
taskUnits[i][j] = IloIntervalVar(env, unitTaskTimes[j][i], name);
taskUnits[i][j].setOptional();
taskUnits[i][j].setStartMin(taskReleaseTimes[i]);
taskUnits[i][j].setEndMax(taskDueTimes[i]);
if(!unitTaskAssignment[j][i]) taskUnits[i][j].setAbsent();
totalCost += unitTaskCosts[j][i]*IloPresenceOf(env, taskUnits[i][j]);
}
model.add(IloAlternative(env, dummyTasks[i], taskUnits[i]));
}

for(IloInt j = 0; j < numUnits; j++)
{
unitTasks[j] = IloIntervalVarArray(env, numTasks);
for(IloInt i = 1; i < numTasks; i++)
{
unitTasks[j][i] = taskUnits[i][j];
}
model.add(IloNoOverlap(env, unitTasks[j]));
}

model.add(IloMinimize(env, totalCost));

IloCP cp(model);

cp.setParameter(IloCP::TimeLimit, 20);
if (cp.solve()) 
{
cout << "There's a solution." << endl;
} 
else 
{
cp.out() << "No solution found. " << std::endl;
}
}
catch (IloException & ex) 
{
env.out() << "Caught " << ex << std::endl;
}
env.end();
return 0;
}

也许有一个更好的逻辑可以应用，我很乐意接受关于如何更好地建模问题的建议，但这真的不是问题所在。

问题是，如果我评论掉这一行

model.add(IloNoOverlap(env, unitTasks[j]));

所有东西都能编译并运行良好，但如果我不考虑它，程序就会编译，但seg在执行时会出错。为什么？

以下是valgrind的输出(如果有帮助的话(：

==361075== Memcheck, a memory error detector
==361075== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==361075== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==361075== Command: ./CP_test
==361075== 
! --------------------------------------------------- CP Optimizer 20.1.0.0 --
! Minimization problem - 15 variables, 5 constraints
! TimeLimit            = 20
! Initial process time : 1.00s (0.99s extraction + 0.02s propagation)
!  . Log search space  : 18.3 (before), 18.3 (after)
!  . Memory usage      : 335.4 kB (before), 335.4 kB (after)
! Using parallel search with 8 workers.
! ----------------------------------------------------------------------------
!          Best Branches  Non-fixed    W       Branch decision
0         15                 -
+ New bound is 17.30000
^C==361075== 
==361075== Process terminating with default action of signal 2 (SIGINT)
==361075==    at 0x4882A9A: futex_wait (futex-internal.h:141)
==361075==    by 0x4882A9A: futex_wait_simple (futex-internal.h:172)
==361075==    by 0x4882A9A: pthread_barrier_wait (pthread_barrier_wait.c:184)
==361075==    by 0xCEFA06: IlcParallel::SynchronizedMaster::workerSynchronize(IlcParallel::ThreadWorker*) (in /home/nate/Dropbox/Princeton/Maravelias/DCA_Branch_and_Cut/cplex_implementation/CP_optimizer_test_instance/CP_test)
==361075==    by 0x66F224: IlcParallelEngineI::SynchronizedMaster::workerSynchronize(IlcParallel::ThreadWorker*) (in /home/nate/Dropbox/Princeton/Maravelias/DCA_Branch_and_Cut/cplex_implementation/CP_optimizer_test_instance/CP_test)
==361075==    by 0xCF3B60: IlcParallel::SynchronizedMaster::ThreadIO::workerWaitInput() (in /home/nate/Dropbox/Princeton/Maravelias/DCA_Branch_and_Cut/cplex_implementation/CP_optimizer_test_instance/CP_test)
==361075==    by 0xCF4182: IlcParallel::ThreadWorker::startup() (in /home/nate/Dropbox/Princeton/Maravelias/DCA_Branch_and_Cut/cplex_implementation/CP_optimizer_test_instance/CP_test)
==361075==    by 0xCF5929: IlcThread::CallStartup(void*) (in /home/nate/Dropbox/Princeton/Maravelias/DCA_Branch_and_Cut/cplex_implementation/CP_optimizer_test_instance/CP_test)
==361075==    by 0x487A608: start_thread (pthread_create.c:477)
==361075==    by 0x4D0A292: clone (clone.S:95)
==361075== 
==361075== HEAP SUMMARY:
==361075==     in use at exit: 1,161,688 bytes in 353 blocks
==361075==   total heap usage: 942 allocs, 589 frees, 2,260,411 bytes allocated
==361075== 
==361075== LEAK SUMMARY:
==361075==    definitely lost: 19,728 bytes in 1 blocks
==361075==    indirectly lost: 9,752 bytes in 13 blocks
==361075==      possibly lost: 2,304 bytes in 8 blocks
==361075==    still reachable: 1,129,904 bytes in 331 blocks
==361075==                       of which reachable via heuristic:
==361075==                         stdstring          : 35 bytes in 1 blocks
==361075==         suppressed: 0 bytes in 0 blocks
==361075== Rerun with --leak-check=full to see details of leaked memory
==361075== 
==361075== For lists of detected and suppressed errors, rerun with: -s
==361075== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

欢迎提出任何建议。请注意，我试图在IBM论坛上发帖，但由于某种原因，我显然没有得到许可。

Answer 1

由于数组初始化循环从1开始，unitTasks[j][0]为空指针，因此出现分段错误。此外，您应该尝试在调试模式下编译(不带-DNDEBUG(，因此在使用null句柄时会出现断言失败。