Xpress Update 8.4.2 is now available on Box.com for Windows, Linux and Mac, from
This is the latest update for the Xpress 8.4 release branch. Please note that it must be installed over a prior installation of FICO Xpress 8.4 and requires a valid Xpress 8.4 license.
* Compiler Library - an issue has been resolved in the handling of conversions in string concatenations
* xprmsrv - windows: server no longer reports unjustified timeouts when starting instances
* Fixed a performance issue with diving heuristics that in some rare cases could trigger an unnecessarily long reoptimization solve.
* Fixed an issue that could result in a too high lower bound being returned for a MIP that was solved to completion during re-presolving.
* Fixed an issue where the tuner may stop prematurely when tuning a problem set without logging.
* Improved consistency of the barrier solver on different platforms.
* XPRSgetlastbarsol should now work when barrier was used in a concurrent solve.
* Improved performance of local search heuristics for problems with Special Ordered Sets (SOS).
* Fixed an issue which could cause a crash in the primal simplex.
* Fixed an issue that would prevent creation of a problem with rows and columns within the limits set by the Community license.
* Added missing method xpress.problem.nlpoptimize() to solve nonlinear optimization problems with the Xpress Python interface.
* Fixed an issue that could lead to a deadlock in the Python interface when using xpress.problem.mipoptimize() with callback functions.
* Fixed a memory leak in the modeling constructs of the Python interface.
* Improved local search heuristics for MINLP problems.
* Improved relative infeasibility checks when XSLP_FILTER bit 1 is enabled.
* The SLP iteration solution refiner will now check for change in relative primal infeasibility.
* Added missing Knitro max nodes control export.
* XSLP_MIPITER now applies to the SLP-MIP-SLP and MIP-in-SLP heuristics as well.
* New fallback strategy for problems instable in linear presolve due to cascading structures.
* Fixed an issue in the ‘produces()‘ constraints