Fix dual flip after postsolve - #3248
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August 31, 2026 15:37
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Additional details and impacted files@@ Coverage Diff @@
## latest #3248 +/- ##
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+ Coverage 73.16% 73.24% +0.07%
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Files 430 445 +15
Lines 103967 108107 +4140
Branches 16719 17325 +606
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+ Hits 76067 79182 +3115
- Misses 27624 28649 +1025
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fwesselm
approved these changes
Sep 1, 2026
| REQUIRE( | ||
| doubleEqual(solution.row_dual[iRow], h.getSolution().row_dual[iRow])); | ||
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| REQUIRE(h.getModelStatus() == HighsModelStatus::kOptimal); |
Collaborator
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Is this duplicate check needed?
| return HighsPostsolveStatus::kNoPrimalSolutionError; | ||
| const bool have_dual_solution = | ||
| presolve_.data_.recovered_solution_.dual_valid; | ||
| const HighsInt report_3040_col = -578; |
Collaborator
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Not related to this branch, but should we keep this?
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Description
When solving a maximization, the costs are flipped before presolve, so that presolve can assume minimization. However, after postsolve, the method to flip duals (
PresolveComponent::negateReducedLpColDuals()) was incorrect, and didn't flip row duals. This is only exposed after primal-dual postsolve, since the dual (and primal) values are recomputed after primal-dual-basis postsolve.There are other errors within primal-dual postsolve, but it's hard to work on them with this error!
Also corrected "successfull" to "successful" in
highs/ipm/hipo/ipm/Solver.cpp@filikatChecklist
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