"Conditional jump or move depends on uninitialised value" for model with SOS 2 and MIP start (master)

[tobiass-sdl]

If the code below is compiled and run with valgrind the following is reported:

==314955== Conditional jump or move depends on uninitialised value(s)
==314955==    at 0x49FA7C1: CbcModel::setBestSolution(CBC_Message, double&, double const*, int) (CbcModel.cpp:14302)
==314955==    by 0x4A64F66: CbcMain1(std::deque<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > >, CbcModel&, CbcParameters&, int (*)(CbcModel*, int), ampl_info*) (CbcSolver.cpp:6700)
==314955==    by 0x4A8B516: CbcMain1(int, char const**, CbcModel&, CbcParameters&, int (*)(CbcModel*, int), ampl_info*) (CbcSolver.cpp:13236)
==314955==    by 0x10EAC6: main (reproduction2.cpp:65)
==314955== 

As far as I can see this is caused by " double obj;" in CbcSolver line 6619 still being uninitialized in line 6700 and then passed to CbcModel::setBestSolution where an if depends on it.

#include "coin-or/CbcModel.hpp"
#include "coin-or/CbcSOS.hpp"
#include "coin-or/CbcSolver.hpp"
#include "coin-or/OsiClpSolverInterface.hpp"

#include <vector>
#include <limits>

int main() {
  int rowCount = 6;
  int columnCount = 8;
  int sosCount = 1;

  double objective[] = {0, 1, 0, 0, 1, 1.8, 2.2, 0};
  int rowIndices[] = {0, 1, 4, 0, 2, 1, 3, 2, 3, 4, 5, 4, 5, 4, 5, 5};
  double values[] = {-1, 1, -1, -1, 1, -1, 1, -1, 1, 1, 1, 3, 1, 5, 1, 1};
  int starts[] = {0, 3, 5, 7, 9, 11, 13, 15, 16};

  double rowLowerBounds[] = {-10, 0, 0, 5, 0, 1};
  double rowUpperBounds[] = {0, 0, 0, 5, 0, 1};
  double colLowerBounds[] = {0, 0, 0, 0, 0, 0, 0, 0};
  double colUpperBounds[] = {std::numeric_limits<double>::max(),
                             std::numeric_limits<double>::max(),
                             std::numeric_limits<double>::max(),
                             std::numeric_limits<double>::max(),
                             1,
                             1,
                             1,
                             1};

  double initialSolution[] = {5, 0, 5, 0, 0, 0, 1, 0};

  int sosIndices[] = {7, 4, 5, 6};
  double sosWeights[] = {0.0, 1, 3, 5};

  OsiClpSolverInterface solver;

  solver.loadProblem(columnCount, rowCount, starts, rowIndices, values,
                     colLowerBounds, colUpperBounds, objective, rowLowerBounds,
                     rowUpperBounds);

  CbcModel model(solver);
  std::vector<std::pair<std::string, double>> sol;
  auto modelSolver = model.solver();

  for (int i = 0; i < columnCount; ++i) {
    const auto val = initialSolution[i];
    sol.emplace_back(modelSolver->getColName(i), val);
  }

  model.setMIPStart(sol);

  OsiObject *sos = new CbcSOS(&model, 4, sosIndices, sosWeights, 0, 2);

  model.addObjects(1, &sos);

  delete sos;

  CbcSolverUsefulData usefulData;
  CbcMain0(model, usefulData);
  std::vector<const char *> argv = {
      "does_not_matter", "-threads", "1",      "-feas", "on", "-seconds", "100",
      "-ratio",          "0.0",      "-solve", "-quit"};

  CbcMain1(argv.size(), argv.data(), model, usefulData);
}

[jjhforrest]

Unable to reproduce as CbcMipStart
gives
Cbc0045I Warning: MIPstart solution is not valid, column names do not match, ignoring it. So code does not follow path which led to undefined obj.

This is a bug arising because there were no integer variables.

I have fixed that. Valgrind does not complain when I run. Changes have been made recently in master which could have fixed problem.

[tobiass-sdl]

Thanks, that commit fixed the unitialized read for me, too.