inconsistent save_non_semi_variable_index in HighsLP of analytic center

[svigerske]

With highs_semibug.lp.txt, we get an error in HighsLp::unapplyMods().
The variable indices stored in this->mods_.save_non_semi_variable_index do not fit to this->integrality_. That is, this->mods_.save_non_semi_variable_index stores an index 49, while this->integrality_ has only 15 entries.
In presolve the MIP gets reduced from 51 to 15 entries.
My guess is that this->mods_ should not be present in this HighsLp (or that it was forgotten to update save_non_semi_variable_index when there are presolve reductions).

==877429== Invalid read of size 1
==877429==    at 0x5F9CACB: HighsLp::unapplyMods() (HighsLp.cpp:519)
==877429==    by 0x5F2D48F: Highs::returnFromRun(HighsStatus, bool) (Highs.cpp:4505)
==877429==    by 0x5F1DD3A: Highs::solve() (Highs.cpp:1705)
==877429==    by 0x5F1A7F2: Highs::run() (Highs.cpp:912)
==877429==    by 0x5FF9EDC: HighsMipSolverData::startAnalyticCenterComputation(highs::parallel::TaskGroup const&)::{lambda()#1}::operator()() const (HighsMipSolverData.cpp:323)
==877429==    by 0x6008A21: HighsTask::Callable<HighsMipSolverData::startAnalyticCenterComputation(highs::parallel::TaskGroup const&)::{lambda()#1}>::operator()() (HighsTask.h:57)
==877429==    by 0x600A2B1: HighsTask::run() (HighsTask.h:117)
==877429==    by 0x600A821: highs::parallel::sync(HighsSplitDeque*) (HighsParallel.h:68)
==877429==    by 0x600A8B8: highs::parallel::TaskGroup::sync() const (HighsParallel.h:90)
==877429==    by 0x5FFA20D: HighsMipSolverData::finishAnalyticCenterComputation(highs::parallel::TaskGroup const&) (HighsMipSolverData.cpp:340)
==877429==    by 0x6003FE5: HighsMipSolverData::evaluateRootNode() (HighsMipSolverData.cpp:2150)
==877429==    by 0x5FDF440: HighsMipSolver::run() (HighsMipSolver.cpp:194)
==877429==  Address 0x690ced1 is 31 bytes before a block of size 16 in arena "client"

(line numbers may be off by 2)

Running HiGHS 1.9.0 (git hash: bdf95f2e0): Copyright (c) 2025 HiGHS under MIT licence terms
MIP  highs_semibug has 50 rows; 51 cols; 142 nonzeros; 11 integer variables; 2 semi-continuous variables
Coefficient ranges:
  Matrix [2e-02, 4e+04]
  Cost   [1e+00, 1e+00]
  Bound  [8e-02, 4e+04]
  RHS    [2e+00, 5e+03]
WARNING: 2 semi-continuous/integer variable(s) have zero lower bound so are continuous/integer
Presolving model
24 rows, 25 cols, 87 nonzeros  0s
14 rows, 25 cols, 67 nonzeros  0s
4 rows, 15 cols, 47 nonzeros  0s

Solving MIP model with:
   4 rows
   15 cols (11 binary, 0 integer, 0 implied int., 4 continuous)
   47 nonzeros

Src: B => Branching; C => Central rounding; F => Feasibility pump; H => Heuristic; L => Sub-MIP;
     P => Empty MIP; R => Randomized rounding; S => Solve LP; T => Evaluate node; U => Unbounded;
     z => Trivial zero; l => Trivial lower; u => Trivial upper; p => Trivial point

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work      
Src  Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

         0       0         0   0.00%   1.1             -inf                 inf        0      0      0         0     0.5s
 R       0       0         0   0.00%   1.1             -73.4740259      101.50%        0      0      0         1     0.9s

[jajhall]

Thanks, I'll investigate

[jajhall]

Fixed by #2143