MPSolver 回调顺序错误

Question

我设置了 MPSolver 的回调，但是当调试变量超出范围时。我减少了测试用例，看起来变量是无序的，但是输出时仍然正确。

问题是它会在更大的输入上运行，并且要求绝对最优是不合理的，所以我仍然需要从回调中获取解决方案。

/*
    IsSolution:1, X1=0, X2=0, X3=1000
    Result:0, X1=1000, X2=0, X3=0
*/
#include "ortools/linear_solver/linear_solver.h"
#include <memory>
#include <iostream>
#include <stdio.h>
using namespace operations_research;

void RangeHelper(MPConstraint* c) {}
template<class ...T>
void RangeHelper(MPConstraint* c, MPVariable* x0, double c0, T... TT) {
  c->SetCoefficient(x0, c0);
  RangeHelper(c, TT...);
}
template<class ...T>
static MPConstraint* Ranger(MPSolver& solver, MPVariable* condition, double RangeL, T... TT) {
  MPConstraint* c = solver.MakeRowConstraint(RangeL, solver.infinity());
  c->SetCoefficient(condition, 1e20);
  RangeHelper(c, TT...);
  return c;
}

struct CMPCBK : MPCallback {
  const MPVariable* X1, * X2, * X3;
  CMPCBK(const MPVariable* X1, const MPVariable* X2, const MPVariable* X3) :
    X1(X1), X2(X2), X3(X3), MPCallback(0, 0) {}
  void RunCallback(MPCallbackContext* r) {
    if (r->Event() == MPCallbackEvent::kMipSolution) {
      printf("IsSolution:%d, X1 = %f, X2 = %f, X3 = %f\n",
        r->CanQueryVariableValues(), r->VariableValue(X1), r->VariableValue(X2), r->VariableValue(X3));
    }
  }
};

int main() {
  std::unique_ptr<MPSolver> solver(MPSolver::CreateSolver("SCIP"));
  const double INF = solver->infinity();
  MPVariable* X1 = solver->MakeNumVar(-INF, INF, "a");
  MPVariable* X2 = solver->MakeNumVar(0, INF, "b");
  MPConstraint* C1 = solver->MakeRowConstraint(0, 0);
  MPVariable* X3 = solver->MakeIntVar(0, 1, "c");
  Ranger(*solver, X3, 1000, X2, -1, X1, 1);
  C1->SetCoefficient(X3, 1);
  MPObjective* obj = solver->MutableObjective();
  obj->SetCoefficient(X1, 1);
  obj->SetMinimization();
  CMPCBK mpcbk(X1, X2, X3);
  solver->SetCallback(&mpcbk);
  printf("Result:%d, ", solver->Solve());
  printf("X1 = %f, X2 = %f, X3 = %f\n",
    X1->solution_value(), X2->solution_value(), X3->solution_value());
}