Xpress Updates 9.8.2

Community Manager

1 month ago

Xpress Updates 9.8.2 is now available on the client area for Windows, Linux, and MacOS on x86-64, and Linux and MacOS on AArch64, from
https://clientarea.xpress.fico.com/download_patch.php#982

This is the latest update for the Xpress 9.8 release branch, respectively, and require matching licenses. Please note that these archives must be extracted over a prior installation of FICO Xpress 9.8, respectively.

Release Notes for 9.8.2

Xpress Optimizer 46.01.03

Fixed an issue with presolve LP folding that could result in memory corruption.
Fixed an issue with single variable indicator bounds during a MIP restart.
Fixed a threading deadlock in the context of loading violated delayed rows.
Fixed a problem in the tuner when tuning probsets and reusing the history where the wrong number of tuner runs was read from the history.
Calling XPRSscale after solving a MIP should now scale the incumbent MIP solution correctly.
Fixed a potential crash in dual KKT simplex.
Fixed an issue when XPRSchgcoltype is used for changing a semi-continuous variable into a semi-integer variable, which could have left the column in an inconsistent state.
Fixed an issue in presolve where in some edge cases incorrect fixings could be produced from quadratic or indicator rows.
Fixed the problem detection for tuning with multiple instances to correctly distinguish LP and MIP problem sets.
Fixed an issue with primal simplex where a slightly infeasible solution could be returned.
Fixed an issue in MIP presolve dual reductions that in some corner cases could lead to a wrong node cutoff during the branch-and-bound tree search.
Fixed an issue with the tuner that in some cases did not use its history.
Adjusted primal simplex to accept small shifted infeasibilities instead of rejecting the solution as unstable.
Fixed an issue in background tasks that in some corner cases could lead to a non-determinism in the solution process when heuristic emphasis is activated (i.e., when the control HEUREMPHASIS is set to value 1 or value 2).
Fixed an issue in IIS that in some rare cases could lead to a crash.
Fixed a memory leak in primal KKT simplex.
Fixed an issue when KKT simplex ran into a worklimit.

Xpress Nonlinear 46.01.03

Fixed an issue in MISLP heuristics for problems with convex quadratic objective.
Fixed an issue with nonlinear eliminations in the presence of indicator constraints.
Fixed an issue where MISLP could erroneously be called after continuing a continuous SLP solve using XPRSoptimize.
Fixed an issue where solutions did not get postsolved correctly if the multistart-winning job ran into a work limit.
Fixed an issue where an initial infeasible multistart job could remain the winner.
Fixed an issue where XPRSgetnlpsol and XPRSgetcallbacksol would return linearization instead of nonlinear slacks when presolve was disabled.
Introduced XSLPsetinitstepbounds to replace missing functionality from XSLPaddvars.
Avoid printing automatically set mps- and inputtol controls in dumpcontrols.
Fixed a potential stack overflow in nonlinear presolve for deeply nested formulas.
Fixed an issue when both the extended final summary and LP logs were enabled.
Fixed an issue where indicator constraints, including ones generated through transformations, were provided to Knitro as hard constraints.
Fixed an issue where postsolve and validate could potentially delete an equalscolumn that was already present in the input problem.
Fixed an issue where linear coefficients added to a nonlinear variable after adding an SLP coefficient to it (not a regular formula) could be ignored.
Fixed an issue with nonlinear indicators that could lead to the basis being lost and incorrect slacks being returned for the indicator.
Fixed an issue with indicator constraints in nonlinear problems when (nonlinear) presolve is off.
Fixed an issue where when following up a global solve that required a bounding box with a convex-quadratic/linear solve that required nonlinear postsolve, the BOUNDINGBOXAPPLIED attribute was not reset properly.
Fixed an issue where fractional initial points or cascaded solutions could be accepted in MIP-in-SLP.

Xpress Global 46.01.03

Fixed an issue in presolve where in some cases incorrect fixings could be produced from quadratic rows.

Xpress Interfaces 46.01.03 (Python, R, Matlab, .NET, Java, C++, C)

Python
- Fixed an issue where messages from the nonlinear solvers were not sent to a callback registered with problem.addMessageCallback.
- Fixed "Variable has no value" error when passing a dict keyed by var objects to xpress.evaluate().
- Nonlinear indicator constraints are now accepted by the Python API.
Java, C#
- Fixed a small problem in examples that use the solution pool.