source: sasmodels/doc/ref/gpu/gpu_computations.rst @ 7e74ed5

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Last change on this file since 7e74ed5 was 7e74ed5, checked in by wojciech, 7 years ago

OpenCL dialog doc updated

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[066f296]1.. _models-computation:
[1875f4e]2
[886fa25]3****************
4GPU Computations
5****************
[1875f4e]6SasView model evaluations can run on your graphics card (GPU) or they can run
[3f5a566]7on the processor (CPU). In general, calculations performed on the GPU will run faster.
[1875f4e]8
9To run on the GPU, your computer must have OpenCL drivers installed.
[711f17e]10For information about OpenCL installation see this
11:ref:`opencl-installation` guidance.
[1875f4e]12
13Where the model is evaluated is a little bit complicated.
14If the model has the line *single=False* then it requires double precision.
15If the GPU is single precision only, then it will try running via OpenCL
16on the CPU.  If the OpenCL driver is not available for the CPU then
17it will run as a normal program on the CPU.
[711f17e]18
[1875f4e]19For models with a large number of parameters or with a lot of code,
20the GPU may be too small to run the program effectively.
21In this case, you should try simplifying the model, maybe breaking it
[711f17e]22into several different modules so that you don't need *IF* statements in your code.
[1875f4e]23If it is still too big, you can set *opencl=False* in the model file and
24the model will only run as a normal program on the CPU.
25This will not usually be necessary.
26
[711f17e]27Device Selection
28................
[1875f4e]29If you have multiple GPU devices you can tell SasView which device to use.
30By default, SasView looks for one GPU and one CPU device
31from available OpenCL platforms.
32
[7e74ed5]33OpenCL devices can be set from OpenCL options dialog in Fitting menu or as
34enviromental variables.
35
36**If you don't want to use OpenCL, you can select "No OpenCL" option from**
37**GUI dialog or set *SAS_OPENCL=None* in your environment settings**
38**This will only use normal programs.**
39
[711f17e]40SasView prefers AMD or NVIDIA drivers for GPU, and prefers Intel or
41Apple drivers for CPU. Both GPU and CPU are included on the assumption that CPU
42is always available and supports double precision.
[1875f4e]43
44The device order is important: GPU is checked before CPU on the assumption that
45it will be faster. By examining ~/sasview.log you can see which device SasView
46chose to run the model.
[711f17e]47
[7e74ed5]48If you want to use one of the other devices, you can select it from OpenCL
49options dialog (accessible from Fitting menu) or run the following from
50the python console in SasView::
[1875f4e]51
52    import pyopencl as cl
53    cl.create_some_context()
54
55This will provide a menu of different OpenCL drivers available.
56When one is selected, it will say "set PYOPENCL_CTX=..."
57Use that value as the value of *SAS_OPENCL*.
58
[711f17e]59Compiler Selection
60..................
[1875f4e]61For models run as normal programs, you may need to specify a compiler.
62This is done using the SAS_COMPILER environment variable.
63Set it to *tinycc* for the tinycc compiler, *msvc* for the
64Microsoft Visual C compiler, or *mingw* for the MinGW compiler.
65TinyCC is provided with SasView so that is the default.
66If you want one of the other compilers, be sure to have it available
[711f17e]67in your *PATH* so SasView can find it!
68
69
70.. note::
71    This help document was last changed by Steve King, 08Oct2016
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