C++ AMP: Accelerated Massive Parallelism with Microsoft® Visual C++® by Kate Gregory & Ade Miller

Author:Kate Gregory & Ade Miller [Kate Gregory and Ade Miller]
Language: eng
Format: epub
Tags: COMPUTERS / Programming / Parallel
ISBN: 9780735664715
Publisher: Microsoft Press
Published: 2012-09-20T00:00:00+00:00

The total element count must be a multiple of the product of the tile size and the tile count.

This code sets up the appropriate constants and checks them:

const size_t elementCount = 16 * 1024 * 1024; const int tileSize = 512; const int tileCount = 128; // Used in cascading reductions // Make sure that elements can be split into tiles so the number of // tiles in any dimension is less than 65536. static_assert((elementCount / tileSize < 65536), "Workload is too large or tiles are too small. This will cause runtime errors."); static_assert((elementCount % (tileSize * tileCount) == 0), "Tile size and count are not matched to element count."); static_assert((elementCount != 0), "Number of elements cannot be zero."); static_assert((elementCount <= UINT_MAX), "Number of elements is too large."); std::wcout << "Running kernels with " << elementCount << " elements, " << elementCount * sizeof(int) / 1024 << " KB of data ..." << std::endl; std::wcout << "Tile size: " << tileSize << std::endl; std::wcout << "Tile count: " << tileCount << std::endl; if (!validateSizes(tileSize, elementCount)) std::wcout << "Tile size is not factor of element count." << std::endl;

Why check values that are hard-coded? A common use for this sample code is to experiment and tweak various settings. You might try increasing or decreasing the workload, for example, or making the tiles larger or smaller, but not all combinations of values will meet the constraints mentioned above. A compile time check and warning will remove some of the mystery from the process. When a static_assert fails, the build fails and you can’t run the application. If you want to trigger the run-time errors in order to see what they look like, comment out the static_assert statements before you build and run the application with invalid values.

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