chore: bump highspy from 1.13.1 to 1.15.0

[dependabot]

Bumps highspy from 1.13.1 to 1.15.0.

Release notes

Sourced from highspy's releases.

v1.15.0

The highlights of v1.15 are the first variant of the parallel MIP solver and the addition of HiPO in Python.

Code changes

Following [PR #2886](ERGO-Code/HiGHS#2886), our prototype multithreaded MIP solver is available, refactoring the worker/node-search logic of the branch-and-cut solver to run across multiple threads. This is the first release of the parallel MIP solver.

A fix to the parallel scheduler was merged in [PR #3087](ERGO-Code/HiGHS#3087).

Following [PR #2994](ERGO-Code/HiGHS#2994), HiPO can now be used to solve LPs and QPs from highspy, with documentation added in [PR #3024](ERGO-Code/HiGHS#3024) and [PR #3060](ERGO-Code/HiGHS#3060). HiPO performance was further improved by faster handling of free variables ([PR #3013](ERGO-Code/HiGHS#3013)) and faster triangular solves ([PR #3014](ERGO-Code/HiGHS#3014)).

Prompted by #2957, square Hessians that are only slightly asymmetric are now accepted by Highs::qFormatOk, rather than being rejected outright ([PR #2965](ERGO-Code/HiGHS#2965), [PR #2984](ERGO-Code/HiGHS#2984) and [PR #3003](ERGO-Code/HiGHS#3003)). Identification of non-convexity in the QP solvers was also improved, with extended documentation added in [PR #3056](ERGO-Code/HiGHS#3056), and a further bug affecting some QPs was fixed in [PR #3069](ERGO-Code/HiGHS#3069). QP hot start was added in [PR #3089](ERGO-Code/HiGHS#3089).

Following [PR #2982](ERGO-Code/HiGHS#2982), several bugs in the computation of an Irreducible Infeasible Subsystem (IIS) via Highs::getIis were fixed.

Following [PR #3046](ERGO-Code/HiGHS#3046), zero-cost singleton columns are no longer fixed to an infinite bound during HPresolve::dualFixing, and the size of shifts applied during reduced-cost fixing was reduced in [PR #2986](ERGO-Code/HiGHS#2986). Strengthened variable bounds found during presolve are now retained ([PR #3010](ERGO-Code/HiGHS#3010)), a bug in the computation of the fractional value of a variable with finite

... (truncated)

Commits

• 8396001 Merge pull request #3103 from ERGO-Code/latest
• 9713e3d Merge pull request #3102 from ERGO-Code/bazel-hconfig
• 05b4fef Merge pull request #3101 from ERGO-Code/latest
• dfd5cbf hconfig
• 413d570 Merge pull request #3100 from ERGO-Code/version-bump-1.15
• 60bfcc8 Updated docs/src/options/definitions.md
• 2af0759 Merge remote-tracking branch 'origin/nix-updates' into version-bump-1.15
• d34765b version bump
• e18790b nix and tests
• 6d870e3 Merge pull request #3096 from ERGO-Code/features-1.15
• Additional commits viewable in compare view

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