Method undo

highs/presolve/HighsPostsolveStack.h:611–777

undo presolve steps for primal dual solution and basis

  /// undo presolve steps for primal dual solution and basis
  void undo(const HighsOptions& options, HighsSolution& solution,
            HighsBasis& basis, const HighsInt report_col = -1,
            const bool thread_safe = false) {
    HighsDataStack reductionValuesCopy;
    std::vector<Nonzero> colValuesCopy;
    std::vector<Nonzero> rowValuesCopy;
    if (!thread_safe) {
      reductionValues.resetPosition();
    } else {
      reductionValuesCopy = reductionValues;
      reductionValuesCopy.resetPosition();
      colValuesCopy = colValues;
      rowValuesCopy = rowValues;
    }
    HighsDataStack& reductionValues_ =
        thread_safe ? reductionValuesCopy : reductionValues;
    std::vector<Nonzero>& colValues_ = thread_safe ? colValuesCopy : colValues;
    std::vector<Nonzero>& rowValues_ = thread_safe ? rowValuesCopy : rowValues;

    // Verify that undo can be performed
    assert(solution.value_valid);
    bool perform_dual_postsolve = solution.dual_valid;
    bool perform_basis_postsolve = basis.valid;

    // expand solution to original index space
    assert(origNumCol > 0);
    undoIterateBackwards(solution.col_value, origColIndex, origNumCol);

    assert(origNumRow >= 0);
    undoIterateBackwards(solution.row_value, origRowIndex, origNumRow);

    if (perform_dual_postsolve) {
      // if dual solution is given, expand dual solution and basis to original
      // index space
      undoIterateBackwards(solution.col_dual, origColIndex, origNumCol);

      undoIterateBackwards(solution.row_dual, origRowIndex, origNumRow);
    }

    if (perform_basis_postsolve) {
      // if basis is given, expand basis status values to original index space
      undoIterateBackwards(basis.col_status, origColIndex, origNumCol);

      undoIterateBackwards(basis.row_status, origRowIndex, origNumRow);
    }

    // now undo the changes
    for (size_t i = reductions.size(); i > 0; --i) {
      if (report_col >= 0)
        printf("Before  reduction %2d (type %2d): col_value[%2d] = %g\n",
               int(i - 1), int(reductions[i - 1].first), int(report_col),
               solution.col_value[report_col]);
      switch (reductions[i - 1].first) {
        case ReductionType::kLinearTransform: {
          LinearTransform reduction;
          reductionValues_.pop(reduction);
          reduction.undo(options, solution);
          break;