Solves adlittle with slack removed

ERGO-Code · Nov 8, 2024 · b14bbe1 · b14bbe1
1 parent d5ffacc
commit b14bbe1
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Showing 3 changed files with 30 additions and 24 deletions.
diff --git a/src/presolve/HPresolve.cpp b/src/presolve/HPresolve.cpp
@@ -4404,17 +4404,13 @@ HPresolve::Result HPresolve::removeSlacks(HighsPostsolveStack& postsolve_stack)
     assert(coeff);
     // Slack is s = (rhs - a^Tx)/coeff
     //
-    if (coeff > 0) {
-      // Constraint bounds become [rhs - coeff * lower, rhs - coeff *
-      // upper]
-      model->col_lower_[iCol] = rhs - coeff * lower;
-      model->col_upper_[iCol] = rhs - coeff * upper;
-    } else {
-      // Constraint bounds become [rhs - coeff * upper, rhs - coeff *
-      // lower]
-      model->col_lower_[iCol] = rhs - coeff * upper;
-      model->col_upper_[iCol] = rhs - coeff * lower;
-    }
+    // Constraint bounds become:
+    //
+    // For coeff > 0 [rhs - coeff * upper, rhs - coeff * lower]
+    //
+    // For coeff < 0 [rhs - coeff * lower, rhs - coeff * upper]
+    model->row_lower_[iRow] = coeff > 0 ? rhs - coeff * upper : rhs - coeff * lower;
+    model->row_upper_[iRow] = coeff > 0 ? rhs - coeff * lower : rhs - coeff * upper;
     if (cost) {
       // Cost is (cost * rhs / coeff) + (col_cost - (cost/coeff) row_values)^Tx
       double multiplier = cost / coeff;
@@ -4426,8 +4422,9 @@ HPresolve::Result HPresolve::removeSlacks(HighsPostsolveStack& postsolve_stack)
       model->offset_ += multiplier * rhs;
     }
     // 
-    postsolve_stack.slackColSubstitution(iRow, iCol, rhs, cost, lower, upper, coeff,
-                                        getColumnVector(iCol));
+    postsolve_stack.slackColSubstitution(iRow, iCol, rhs, cost, lower, upper, //coeff,
+					 getRowVector(iRow),
+					 getColumnVector(iCol));
     markColDeleted(iCol);
 
     unlink(coliter);

diff --git a/src/presolve/HighsPostsolveStack.cpp b/src/presolve/HighsPostsolveStack.cpp
@@ -1356,11 +1356,14 @@ void HighsPostsolveStack::SlackColSubstitution::undo(
     const std::vector<Nonzero>& colValues, HighsSolution& solution,
     HighsBasis& basis) {
 
-    assert(111==222);
-
-
-
+  // Taken from HighsPostsolveStack::FreeColSubstitution::undo(
+  //
   // a (removed) cut may have been used in this reduction.
+  //
+  // May have to determine row dual and basis status unless doing
+  // primal-only transformation in MIP solver, in which case row may
+  // no longer exist if it corresponds to a removed cut, so have to
+  // avoid exceeding array bounds of solution.row_value
   bool isModelRow = static_cast<size_t>(row) < solution.row_value.size();
 
   // compute primal values
@@ -1375,9 +1378,9 @@ void HighsPostsolveStack::SlackColSubstitution::undo(
 
   assert(colCoef != 0);
   // Row values aren't fully postsolved, so why do this?
-  if (isModelRow)
-    solution.row_value[row] =
+  if (isModelRow) solution.row_value[row] =
         double(rowValue + colCoef * solution.col_value[col]);
+  printf("HighsPostsolveStack::SlackColSubstitution::undo rowValue = %g\n", double(rowValue));
   solution.col_value[col] = double((rhs - rowValue) / colCoef);
 
   // if no dual values requested, return here

diff --git a/src/presolve/HighsPostsolveStack.h b/src/presolve/HighsPostsolveStack.h
@@ -224,7 +224,7 @@ class HighsPostsolveStack {
     double colCost;
     double colLower;
     double colUpper;
-    double colCoeff;
+    //    double colCoeff;
     HighsInt row;
     HighsInt col;
 
@@ -339,16 +339,22 @@ class HighsPostsolveStack {
     reductionAdded(ReductionType::kFreeColSubstitution);
   }
 
-  template <typename ColStorageFormat>
+  template <typename RowStorageFormat, typename ColStorageFormat>
   void slackColSubstitution(HighsInt row, HighsInt col, double rhs,
-			    double colCost, double colLower, double colUpper, double colCoeff, 
+			    double colCost, double colLower, double colUpper, //double colCoeff,
+			    const HighsMatrixSlice<RowStorageFormat>& rowVec, 
 			    const HighsMatrixSlice<ColStorageFormat>& colVec) {
+    rowValues.clear();
+    for (const HighsSliceNonzero& rowVal : rowVec)
+      rowValues.emplace_back(origColIndex[rowVal.index()], rowVal.value());
+
     colValues.clear();
     for (const HighsSliceNonzero& colVal : colVec)
       colValues.emplace_back(origRowIndex[colVal.index()], colVal.value());
 
-    reductionValues.push(SlackColSubstitution{rhs, colCost, colLower, colUpper, colCoeff, origRowIndex[row],
-                                             origColIndex[col]});
+    reductionValues.push(SlackColSubstitution{rhs, colCost, colLower, colUpper, //colCoeff,
+					      origRowIndex[row],
+					      origColIndex[col]});
     reductionValues.push(rowValues);
     reductionValues.push(colValues);
     reductionAdded(ReductionType::kSlackColSubstitution);