OpenCL: Difference between revisions
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===Linux=== | ===Linux=== | ||
https://gist.github.com/Brainiarc7/dc80b023af5b4e0d02b33923de7ba1ed | https://gist.github.com/Brainiarc7/dc80b023af5b4e0d02b33923de7ba1ed | ||
<pre> | |||
sudo apt install ocl-icd-opencl-dev opencl-headers | |||
sudo apt install opencl-c-headers opencl-clhpp-headers | |||
</pre> | |||
==Getting Started== | ==Getting Started== | ||
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See https://www.eriksmistad.no/getting-started-with-opencl-and-gpu-computing/ | See https://www.eriksmistad.no/getting-started-with-opencl-and-gpu-computing/ | ||
{{hidden | C example | | |||
vector_add_kernel.cl | |||
<syntaxhighlight lang="c"> | <syntaxhighlight lang="c"> | ||
__kernel void vector_add(__global const int *A, __global const int *B, __global int *C) { | __kernel void vector_add(__global const int *A, __global const int *B, __global int *C) { | ||
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} | } | ||
</syntaxhighlight> | </syntaxhighlight> | ||
<syntaxhighlight lang="c"> | <syntaxhighlight lang="c"> | ||
#include <stdio.h> | #include <stdio.h> | ||
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===C++=== | ===C++=== | ||
[https://github.khronos.org/OpenCL-CLHPP/index.html#intro C++ Bindings]<br> | [https://github.khronos.org/OpenCL-CLHPP/index.html#intro C++ Bindings]<br> | ||
While you can use the C bindings in your C++ application, Khronos also provides a set of C++ bindings in <code>CL/cl2.hpp</code> which are much easier to use alongside std containers such as <code>std::vector</code>. When using C++ bindings, you also do not need to worry about releasing buffers since these are reference-counted. | While you can use the C bindings in your C++ application, Khronos also provides a set of C++ bindings in <code>CL/cl.hpp</code> (or <code>CL/cl2.hpp</code>) which are much easier to use alongside std containers such as <code>std::vector</code>. | ||
When using C++ bindings, you also do not need to worry about releasing buffers since these are reference-counted. | |||
{{hidden | C++ example | | {{hidden | C++ example | | ||
<syntaxhighlight lang="cpp"> | <syntaxhighlight lang="cpp"> | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
}} | }} | ||
===Python=== | |||
See [https://documen.tician.de/pyopencl/index.html pyopencl]. | |||
===Julia=== | ===Julia=== | ||
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==Usage== | ==Usage== | ||
===Types=== | ===Scalar Types=== | ||
[https://www.khronos.org/registry/OpenCL/sdk/1. | [https://www.khronos.org/registry/OpenCL/sdk/1.2/docs/man/xhtml/scalarDataTypes.html OpenCL 1.2 Scalar Data Types]<br> | ||
While all OpenCL devices support single-precision floats, not all support double-precision doubles.<br> | While all OpenCL devices support single-precision floats, not all support double-precision doubles.<br> | ||
===Vector Types=== | |||
[https://www.khronos.org/registry/OpenCL/sdk/1.2/docs/man/xhtml/dataTypes.html OpenCL Data Types]<br> | |||
[https://www.khronos.org/registry/OpenCL/sdk/1.2/docs/man/xhtml/vectorDataTypes.html OpenCL 1.2 Vector Data Types]<br> | |||
Just like glsl, OpenCL supports vector types such | Just like glsl, OpenCL supports vector types such | ||
<syntaxhighlight lang="c">float3 my_vec = (float3)(1.0);</syntaxhighlight> | <syntaxhighlight lang="c">float3 my_vec = (float3)(1.0);</syntaxhighlight> | ||
where its elements are accessed using x,y,z as <code>my_vec.x</code>.<br> | where its elements are accessed using x,y,z as <code>my_vec.x</code>.<br> | ||
To convert between vector types, use <code>convert_T()</code><br> | To convert between vector types, use <code>convert_T()</code><br> | ||
;Notes | |||
* 3-component data types are aligned to 4 components. I.e. an array of <code>uchar3</code> with 4 elements will be equivalent to an array of <code>uchar4</code> with 4 elements. | |||
==OpenGL Interop== | |||
Setting up OpenCL/OpenGL interop is fairly complicated and very hard to debug. | |||
You will also need to manage synchronizing OpenGL/OpenCL so they do not access the same memory at the same time. | |||
If you can, just use OpenGL compute shaders rather than OpenCL to simplify your life. | |||
===Textures=== | |||
See [https://software.intel.com/content/www/us/en/develop/articles/opencl-and-opengl-interoperability-tutorial.html OpenCL™ and OpenGL* Interoperability Tutoria]. | |||
In C++, you can use [https://github.khronos.org/OpenCL-CLHPP/classcl_1_1_image_g_l.html <code>cl::ImageGL</code>] to access textures in OpenGL. | |||
Note that <code>cl::Image</code> and <code>cl::Buffer</code> are not the same thing. Interchanging them will result in <code>CL_INVALID_MEM_OBJECT</code> errors or similar. | |||
I recommend writing to a separate buffer and copying to images. | |||
See [https://www.khronos.org/registry/OpenCL/sdk/2.2/docs/man/html/clCreateFromGLTexture.html clCreateFromGLTexture] to get a list of compatible pixel formats. | |||
If in doubt, use <code>GL_RGBA8</code> which is the most likely format to be supported. | |||
===Buffers=== | |||
[https://web.engr.oregonstate.edu/~mjb/cs575/Handouts/opencl.opengl.vbo.1pp.pdf Oregon State VBO Interop] | |||
[https://github.khronos.org/OpenCL-CLHPP/classcl_1_1_buffer_g_l.html cl::BufferGL] | |||
==Advanced Topics== | ==Advanced Topics== | ||
====Local Memory v. Global Memory==== | ====Local Memory v. Global Memory==== | ||
[[Category:Programming languages]] | |||
[[Category:GPU Programming languages]] | |||