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OpenCL SYCL BOF - SIGGRAPH 2014
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OpenCL SYCL BOF - SIGGRAPH 2014

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SYCL slide presentation from the 2014 SIGGRAPH BOF

SYCL slide presentation from the 2014 SIGGRAPH BOF

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  • 1. © Copyright Khronos Group 2014 SYCL™ for OpenCL™ in a Nutshell Luke Iwanski, Games Technology Programmer @ Codeplay ! SIGGRAPH Vancouver 2014 1
  • 2. 2 © Copyright Khronos Group 2014
  • 3. © Copyright Khronos Group 2014 SYCL for OpenCL in a nutshell • Why? • Where in the OpenCL ecosystem? • Motivation • Features overview • Example time • Roadmap 3
  • 4. © Copyright Khronos Group 2014 Why SYCL? • Modern C++ programming model for OpenCL (compiler, runtime) • Ease to use • High performance • Single source • Allows multi-compiler implementation. SYCL device compiler + Host compiler of your choice • Portability across platforms and compilers • Providing the full OpenCL feature set and seamless integration with existing OpenCL code • Enabling the creation of higher level programming models and C++ templated libraries based on OpenCL 4
  • 5. © Copyright Khronos Group 2014 Alternative Language for Alternative Language for Alternative Language Kernels for SPIR Generator (e.g. Khronos patched Clang open source on GitHUB) Kernels Kernels Device X Device Y Device Z High-level HFirgahm-leewveolr ks AFprapms eawndo rks Frameworks ! OpenCL Runtime SPIR Standard Portable Intermediate Representation SPIR 1.2 Released January 2014 SYCL A programming abstraction that combines the portability and efficiency of OpenCL with the ease of use and flexibility of C++ SYCL 1.2 Provisional Released March 2014 OpenCL ecosystem OpenCL C Kernel Source 5
  • 6. © Copyright Khronos Group 2014 The layering of SYCL: Building an ecosystem User application code C++ template libraries SYCL for OpenCL OpenCL 6
  • 7. © Copyright Khronos Group 2014 Motivation • We want to enable C++ for the OpenCL ecosystem • Where more C++ developers can get the benefits of OpenCL • With C++ libraries supported on OpenCL platforms • C++ tools supported on OpenCL platforms • Aim to achieve long-term support for OpenCL features with C++ • Multiple Sources of implementations (multiple vendors) • Reliability by providing host fall-back • Enable future innovations 7
  • 8. © Copyright Khronos Group 2014 SYCL features: Overview 8
  • 9. © Copyright Khronos Group 2014 • OpenCL/SYCL interoperability • Seamless integration of OpenCL C applications with SYCL applications • OpenCL C data types and built-in functions available • SYCL / OpenGL interoperability • Based on OpenCL/OpenGL interoperability extensions • C++ exception handling • Host “fall-back” mode - using SYCL without OpenCL • Introduced in SYCL Hierarchical data parallelism 9
  • 10. © Copyright Khronos Group 2014 Hierarchical Data Parallelism buffer<int> my_buffer(data, 10); auto in_access = my_buffer.get_access<cl::sycl::access:read>(); a!uto out_access = my_buffer.access<cl::sycl::access:write>(); command_group(my_queue, [&]() { " parallel_for_workgroup(nd_range(range(size), range(groupsize)), " " lambda<class hierarchical>([=](group group) " { " " parallel_for_workitem(group, [=](item tile) " " { " " " out_access[tile] = in_access[tile] * 2; " " }); " })); }); Task (nD-range) Workgroup Work item Work item Workgroup Work item Work item Work item Workgroup Work Work item item Work item Workgroup Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Work item Advantages:! 1. Easy to understand the concept of work-groups! 2. Performance-portable between CPU and GPU! 3. Barriers are automatically deduced!! 4. Easier to compose components and algorithms 10
  • 11. © Copyright Khronos Group 2014 Example time: Simple kernel 11
  • 12. 12 © Copyright Khronos Group 2014
  • 13. 13 © Copyright Khronos Group 2014 Simple kernel summary • Simple kernel demo source is only 20 lines of actual C++/ SYCL code • Equivalent of simple kernel demo in OpenCL takes over 100 lines of code • This code can be easily templated by changing 17 lines of code • Plain OpenCL C will take many, many, .. many more lines of code
  • 14. © Copyright Khronos Group 2014 Example time: Templated kernel 14
  • 15. 15 © Copyright Khronos Group 2014
  • 16. 16 © Copyright Khronos Group 2014
  • 17. 17 © Copyright Khronos Group 2014
  • 18. 18 © Copyright Khronos Group 2014 Templated kernel summary • Only 52 lines of code to create a templated kernel for the subtract operation! • Templates on the device! • factor of 5 lines per new datatype! (including initialisation and printing) • SYCL is simple!!
  • 19. 19 © Copyright Khronos Group 2014 Final notes about SYCL • Keep in mind • Advantages of modern C++ (lambdas, templates, struct arguments, static polymorphism) • but, limitations of current OpenCL ( recursion, dynamic allocation, static variables) • It will get better with the next OpenCL iterations!
  • 20. © Copyright Khronos Group 2014 • GDC, March 2014 SYCL roadmap • Released a provisional specification to enable feedback • Developers can provide input into the standardisation process • Feedback via Khronos forums • Next steps • Full specification, based on feedback • Khronos test suite for implementations • Release of implementations 20
  • 21. © Copyright Khronos Group 2014 SYCL Useful Links • SYCL spec and forums: • http://www.khronos.org/opencl/sycl • triSYCL github: • https://github.com/amd/triSYCL • Codeplay’s blogs: • http://www.codeplay.com/portal/ • Examples github • https://github.com/codeplaysoftware/Siggraph14.git 21
  • 22. © Copyright Khronos Group 2014 Thanks! Luke Iwanski luke@codeplay.com @liwanski_ 22

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