[14de349] | 1 | """ |
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| 2 | GPU data alignment. |
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| 3 | |
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| 4 | Some web sites say that maximizing performance for OpenCL code requires |
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| 5 | aligning data on certain memory boundaries. |
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| 6 | |
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| 7 | :func:`data_alignment` queries all devices in the OpenCL context, returning |
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| 8 | the most restrictive alignment. |
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| 9 | |
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| 10 | :func:`align_data` aligns an existing array. |
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| 11 | |
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| 12 | :func:`align_empty` to create a new array of the correct alignment. |
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| 13 | |
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| 14 | Note: This code is unused. So far, tests have not demonstrated any |
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| 15 | improvement from forcing correct alignment. The tests should |
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| 16 | be repeated with arrays forced away from the target boundaries |
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| 17 | to decide whether it is really required. |
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| 18 | """ |
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| 19 | |
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| 20 | import numpy as np |
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| 21 | import pyopencl as cl |
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| 22 | |
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| 23 | def data_alignment(context): |
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| 24 | """ |
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| 25 | Return the desired byte alignment across all devices. |
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| 26 | """ |
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| 27 | # Note: rely on the fact that alignment will be 2^k |
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| 28 | return max(d.min_data_type_align_size for d in context.devices) |
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| 29 | |
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| 30 | def align_empty(shape, dtype, alignment=128): |
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| 31 | size = np.prod(shape) |
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| 32 | dtype = np.dtype(dtype) |
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| 33 | # allocate array with extra space for alignment |
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| 34 | extra = alignment//dtype.itemsize - 1 |
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| 35 | result = np.empty(size+extra, dtype) |
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| 36 | # build a view into allocated array which starts on a boundary |
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| 37 | offset = (result.ctypes.data%alignment)//dtype.itemsize |
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| 38 | view = np.reshape(result[offset:offset+size], shape) |
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| 39 | return view |
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| 40 | |
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| 41 | def align_data(v, dtype, alignment=128): |
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| 42 | # if v is contiguous, aligned, and of the correct type then just return v |
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| 43 | view = align_empty(v.shape, dtype, alignment=alignment) |
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| 44 | view[:] = v |
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| 45 | return view |
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| 46 | |
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| 47 | def work_group_size(context, kernel): |
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| 48 | """ |
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| 49 | Return the desired work group size for the context. |
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| 50 | """ |
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| 51 | max(kernel.get_work_group_info(cl.kernel_work_group_info.PREFERRED_WORK_GROUP_SIZE_MULTIPLE, d) |
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| 52 | for d in context.devices) |
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| 53 | |
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| 54 | |
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