Selecting the right hardware can dramatically improve the performance of Xpress-MP.

Xpress-MP is a CPU-intensive application. During the optimization process itself, it operates most efficiently when it has dedicated access to the CPU. If run in conjunction with other applications, or several instances of Xpress-MP are run at once, then the performance of Xpress-MP and any other applications is severely degraded.

We do not need to remind you that computer hardware specifications change very quickly, and the specifications quoted below are subject to continuous change and improvement. However, the factors themselves will remain important.

CPU performance

The single most important characteristic of the hardware is raw CPU speed. The performance of Xpress-MP will scale fairly linearly with effective CPU speed for all sizes of model ( assuming no other constraining factors ).

Xpress-MP currently performs best on the Intel Core CPU architecture. This family of CPUs include the Core 2 desktop CPUs and the new Xeon server CPUs ( the Xeon line is now a mixed architecture line comprised of the old netburst Pentium 4 based Xeons and the new Core based Xeons. Models 30**, 32**, 51** and 53** are the best choices. ).

Desktop recommendations: Intel E6700, X6800, QX6700, QX6800
Server recommendations: Intel 3070, 5150, 5160, X5355, X5365

The absolute minimum processor requirement is an Intel Pentium 3 or equivalent.

Memory considerations

For very small models, quantity and speed of memory will have little or no impact on performance as the data will be cached on the CPU. For models that are larger than the available cache, performance will increase slightly with memory speed. If the amount of memory required by Xpress-MP exceeds the available physical memory then performance will seriously degrade as virtual memory is paged in by the operating system. Avoid this situation if at all possible.

Use of the IVE development environment will double the amount of memory required. Use of Parallel MIP will increase the amount of memory required proportional to the number of threads employed in the solve.

Recommendations: 2GB of memory for 32bit operating systems, 4GB for 64bit operating systems.

Other components

Xpress-MP creates temporary files. The implementation of the I/O routines is such that access speed of the local hard-drive will not perceptably affect the performance of the software. However, we would not recommend these temporary files be directed to considerably slower media such as network drives or usb flash memory.

Operating systems

If performance and cost are the only selection factors then Intel and AMD x86/x64 CPU families, as both the cheapest and fastest mainstream processors available, would be the obvious hardware choice. This restricts the choice of operating system to either Windows or Linux. Our primary development platform is Windows and this is our recommended operating system.

Our full list of support operating systems can be found here.

Parallel Solving

Current Intel multi-core CPUs share a single interface to the main memory which is suitable for users of Parallel MIP ( multiple cores solving the same one problem ). Users who wish to run multiple different non-trivial models concurrently should instead consider a multi-cpu ( multiple CPU sockets on one motherboard ) system to avoid the memory bottleneck inherent in single CPU multi-core machines.

Future AMD CPUs are expected to improve memory access for the single CPU, multi-core architecture.

32bit or 64bit

The 64bit software generally runs 5-15% faster than the equivalent 32bit software ( one exception to this trend is where compilation of a mosel model takes a substantial portion of the overall time, as compiling a model in 64bit Mosel takes slightly longer than in 32bits ). However, the main reason for moving to 64bit is the vastly increased potential available memory.

No matter how much physical memory is installed in a machine, the maximum theoretical amount of memory that a 32bit process can access is 4GB. On 32bit Windows the upper limit is even less at 2GB. Larger models can easily exceed this even without the use of IVE or Parallel MIP.

64bit Windows removes this upper limit ( actually there is still an upper limit but it wont be an issue for decades ). Current RAM prices mean that its quite cheap to populate a machine with 8GB or more and the entire physical memory is available to an Xpress-MP process.

32bit Xpress-MP users who wish to upgrade to the 64bit software should contact their nearest sales office.

For any questions relating to hardware, please contact your nearest support office.