Computer capability and calculation time

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RE: Computer capability and calculation time

Stefanos Papavasileiou

Dear Emmanuel,

With all the rapid changes in computer hardware is very difficult for us to know exactly what is perfect for you. Please check the general recommendations we provide below.

All our recommendations we provide are based on single desktop computers with a natively running Windows 64-bit environment (Windows 10), since this is what we design the software for and run all our tests on. The system requirements are mentioned here: communities.bentley.com/.../system-requirements---plaxis

 To get quick operations in the program:

• make sure the Windows TEMP is stored on a fast disk, e.g. an SSD. During the calculations, the calculation will need to read and write a lot of data so having a fast drive will help overall for the calculation; 
• storing the final data on a normal hard drive does not influence the calculation time: only when you tell Plaxis to save the data, the data from the Windows TEMP folder will be moved to the final save location; 
• have enough RAM. For models up to 500,000 elements not doing dynamic calculations, 16 GB should work. For larger models, get at least 32 GB. Only when you have models with roughly more than 1 million elements 32 GB RAM would be required; 
• For visualization, get a recent (gaming) graphics card that supports OpenGL 2 or higher with at least 1 GB of dedicated, not shared, RAM. Preferably from NVIDIA; 
• From our benchmarking, we did not see a conclusive speed increase for all kinds of calculation types (Plastic, Consolidation, Dynamics, etc.) in the calculation when you have more than 8 cores; 
• Note that we do not use hyperthreading, but Plaxis will utilize all physically available cores. If the processor uses hyperthreading, this is not used. What hyper-threading does, is that splits a core usage into two virtual cores. For a Plaxis calculation, this means that it will try to use 1 at 100% and the other at about 20% (this is managed by Windows and the processor architecture). Then for the Plaxis calculation, the performance of the first one drops a bit too, since one processor cannot be used for 120% (so to run 120% of calculation operations per second). So, the total performance drops a bit too. In general, for a PLAXIS calculation, this runs slower than using the e.g. 4 physical cores to the max, compared to a setup with 4 hyperthreaded cores (8 logical cores). 
• And of course, a faster CPU will mean faster calculations.  

 If you need to make a choice between more CPU cores or faster CPU cores, I would go for the faster cores if your main concern is the Plaxis calculation speed. We have seen once you have at least quad-core processors, you benefit more from a faster CPU than from more cores.

 PLAXIS does not enforce limits on the number of items in a 3D calculation, but of course, the more elements you have, the more memory the program needs, and then you can run into hardware limitations.

 Of course, this is the experience we have with the current program.

 See more details here:

• Hardware: https://communities.bentley.com/products/geotechnical1/w/wiki/45817/multicore-cpu-and-32-64-bit
• Setting up phases efficiently: communities.bentley.com/.../is-plaxis-3d-enabled-for-multicore
  includes info about running parallel phases simultaneously 

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