Xpress patch release 8.1.1

Document created by zsoltcsizmadia@fico.com on Mar 13, 2017
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Xpress patch 8.1.1 is now available on Box for Windows 64 and 32, Linux 64 and Mac 64 from




Xpress-Optimizer 30.01.05 release notes:


* Fixed a problem with nondefault setting REFINEOPS=-1 causing a crash during the MIP search.

* Fixed an issue with the SLX solution file reader.

* Fixed an issue with the logging of the concurrent solver when it uses the dual simplex sifting algorithm.

* Fixed an issue with bound reduction in problems with linear and quadratic terms that may deduce incorrect bounds.

* Fixed an issue in the barrier warmstart when a dual solution is available.

* Fixed an issue that could cause an unexpected termination of the branch-and-bound search.

* Fixed an issue with the rounding heuristics that could result in a violated partial integer solution.

* Fixed an issue with MIP cutoff tightening that could result in valid solutions being dropped.

* Modified probing during presolve to be less costly for MIPs with very large constraints.

* Changing the objective sense (explicitly with XPRSchgobjsense or implicitly by calling XPRSminim/XPRSmaxim) should no longer cause pre-loaded MIP solutions to be dropped.

* Fixed an issue related to trying redundant control settings in the tuner.

* Fixed an issue related to the tuner with non-linear problems.

* Fixed an issue where best runs from the tuner could not be reproduced.

* Introduced a new option -1 for the TUNERTHREADS control. This will set the number of threads used by the tuner to the number of detected logical threads.

* Fixed an issue in the Python interface that might trigger a crash when multiple calls are made to the same API function.


Xpress-Nonlinear 30.01.05 release notes:


* Fixed a convergence issue related to variables appearing in neutral rows.

* Fixed a problem where the setting XSLP_MATRIXTOL was ignored.

* Fixed a problem which could cause an incorrect objective function to be used in an XSLPunconstruct and XSLPconstruct sequence.


This is the latest Xpress update for the Xpress 8.1 release branch. Please note that it must be installed over a prior installation of FICO Xpress 8.1 and requires a valid Xpress 8.1 license.