source: sasview/docs/sphinx-docs/source/user/gpu_computations.rst @ 20a3c55

Last change on this file since 20a3c55 was 6e0c7b2, checked in by wojciech, 5 years ago

Documentation added for gpu computations of sasmodels (related to ticket #572)

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GPU Computations

SasView model evaluations can run on your graphics card (GPU) or they can run on the processor (CPU).

To run on the GPU, your computer must have OpenCL drivers installed. For information about OpenCL installation see the :ref:`opencl-installation` documentation


Where the model is evaluated is a little bit complicated. If the model has the line single=False then it requires double precision. If the GPU is single precision only, then it will try running via OpenCL on the CPU. If the OpenCL driver is not available for the CPU then it will run as a normal program on the CPU. For models with a large number of parameters or with a lot of code, the GPU may be too small to run the program effectively. In this case, you should try simplifying the model, maybe breaking it into several different models so that you don't need if statements in your code. If it is still too big, you can set opencl=False in the model file and the model will only run as a normal program on the CPU. This will not usually be necessary.

If you have multiple GPU devices you can tell SasView which device to use. By default, SasView looks for one GPU and one CPU device from available OpenCL platforms.

It prefers AMD or NVIDIA drivers for GPU, and prefers Intel or Apple drivers for CPU. Both GPU and CPU are included on the assumption that CPU is always available and supports double precision.

The device order is important: GPU is checked before CPU on the assumption that it will be faster. By examining ~/sasview.log you can see which device SasView chose to run the model. If you don't want to use OpenCL, you can set SAS_OPENCL=None in the environment, and it will only use normal programs. If you want to use one of the other devices, you can run the following from the python console in SasView:

import pyopencl as cl

This will provide a menu of different OpenCL drivers available. When one is selected, it will say "set PYOPENCL_CTX=..." Use that value as the value of SAS_OPENCL.

For models run as normal programs, you may need to specify a compiler. This is done using the SAS_COMPILER environment variable. Set it to tinycc for the tinycc compiler, msvc for the Microsoft Visual C compiler, or mingw for the MinGW compiler. TinyCC is provided with SasView so that is the default. If you want one of the other compilers, be sure to have it available on the path so SasView can find it.

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