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Our customers run models of all sizes and levels of difficulty. For some real applications, the models are small and can be solved quickly on even an older, slower computer. Other customers solve models that take hours or even longer to solve. For them, purchasing the fastest computer available is important. Everyone prefers faster computers, of course.
Many GAMS users find it beneficial to have at least two CPUs or a dual core CPU so that their machine can be responsive while running a demanding model. For academic users who have GAMS/CPLEX, GAMS/MOSEK, or GAMS/XPRESS licensed, the advantage is greater since the academic version of these solvers includes the parallel option (4 threads).
GAMS is available in a 32 bit and a 64 bit version for Windows and Linux. The 64 bit Windows version requires the presence of a 64 bit version of Windows to operate properly - just having a 64 bit processor is not sufficient. The 32 bit Windows version of GAMS will work on both versions of Windows, but the operating system limits the GAMS and solver process to approximately 1.7 GB (Windows 32 Bit) or approximately 4 GB (Windows 64 Bit). The 64 bit version of GAMS can address much more memory - only the (physically) available RAM will limit the size of your model. Some NLP solvers still have a limit of 8 GB.
In general, you should not expect a major performance improvement from the 64 bit version. The benefit will be being able to solve larger models. Please note that the 64bit version of GAMS may require up to 35% more RAM than the 32 bit version. Sometimes it may be advantageously to run the 32 bit version of GAMS on a 64 bit version of the operating system.