source: sasmodels/sasmodels/alignment.py @ 0507e09

core_shell_microgelsmagnetic_modelticket-1257-vesicle-productticket_1156ticket_1265_superballticket_822_more_unit_tests
Last change on this file since 0507e09 was 870a2f4, checked in by Paul Kienzle <pkienzle@…>, 7 years ago

fix doc builds

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Line 
1"""
2GPU data alignment.
3
4Some web sites say that maximizing performance for OpenCL code requires
5aligning data on certain memory boundaries.  The following functions
6provide this service:
7
8:func:`align_data` aligns an existing array, returning a new array of the
9correct alignment.
10
11:func:`align_empty` to create an empty array of the correct alignment.
12
13Set alignment to :func:`gpu.environment()` attribute *boundary*.
14
15Note:  This code is unused. So far, tests have not demonstrated any
16improvement from forcing correct alignment.  The tests should
17be repeated with arrays forced away from the target boundaries
18to decide whether it is really required.
19"""
20import numpy as np  # type: ignore
21
22def align_empty(shape, dtype, alignment=128):
23    """
24    Return an empty array aligned on the alignment boundary.
25    """
26    size = np.prod(shape)
27    dtype = np.dtype(dtype)
28    # allocate array with extra space for alignment
29    extra = alignment//dtype.itemsize - 1
30    result = np.empty(size+extra, dtype)
31    # build a view into allocated array which starts on a boundary
32    offset = (result.ctypes.data%alignment)//dtype.itemsize
33    view = np.reshape(result[offset:offset+size], shape)
34    return view
35
36def align_data(x, dtype, alignment=128):
37    """
38    Return a copy of an array on the alignment boundary.
39    """
40    # if x is contiguous, aligned, and of the correct type then just return x
41    view = align_empty(x.shape, dtype, alignment=alignment)
42    view[:] = x
43    return view
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