Xpress Update 8.4.1

Document created by Michael.Perr on Nov 16, 2017Last modified by Michael.Perr on Nov 17, 2017
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Xpress Update 8.4.1 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.


Release Notes:


Mosel 4.8.1:


  • 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


mmssl 1.4.2:


  • Enhancements/updates:
    • new default value for https_ciphers: "TLSv1.2+HIGH:TLSv1+HIGH:@STRENGTH"


mmhttp 2.4.1:


  • Bugs fixed:
    • HTTP headers of responses are now case insensitive


mosjvm 1.0.3:


  • Parameter 'jvmclasspath' can be used to set Java classpath from the Mosel model


Xpress-Optimizer 32.01.04:


  • Fixed an issue where creating ~8500 cones would trigger a crash in the Python interface.
  • Fixed issues where simplex solvers may wrongly declare numerical hard problems infeasible.
  • Ensure that all constraints without variables can be added with the Python interface.
  • Fixed an issue for MIPs that could result in invalid MIR cuts being created.
  • Fixed a numerical issue with rounding heuristics for MIPs with SOS constraints that could result in a solve hanging.
  • Fixed a termination issue with a local search heuristic that could result in an "internal error" message.


Xpress-Nonlinear 32.01.04:


  • Improved barrier fallback strategy for numerically instable solves.
  • The drcoltol handler and callback are now initiated by XSLPconstruct if set up.


Xpress Workbench 2.1.2:


  • Fixed errors when running Mosel models: "died waiting for dll loading, errno 11" and ""Resource temporarily unavailable"