9cfc7967dd
* Replace license text in headers with SPDX identifiers. * Remove specific license info from outdated readme.txt, instead leave details to the source files. * Add list of SPDX license identifiers used, and corresponding license texts. * Update copyright dates while we're at it. Ref D14069, T95597
70 lines
1.7 KiB
C++
70 lines
1.7 KiB
C++
/* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 2008, Frances Y. Kuo and Stephen Joe
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* All rights reserved. */
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/*
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* Sobol sequence direction vectors.
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*
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* This file contains code to create direction vectors for generating sobol
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* sequences in high dimensions. It is adapted from code on this webpage:
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*
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* http://web.maths.unsw.edu.au/~fkuo/sobol/
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*
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* From these papers:
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*
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* S. Joe and F. Y. Kuo, Remark on Algorithm 659: Implementing Sobol's quasirandom
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* sequence generator, ACM Trans. Math. Softw. 29, 49-57 (2003)
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*
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* S. Joe and F. Y. Kuo, Constructing Sobol sequences with better two-dimensional
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* projections, SIAM J. Sci. Comput. 30, 2635-2654 (2008)
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*/
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#include "util/types.h"
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#include "scene/sobol.h"
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CCL_NAMESPACE_BEGIN
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#include "scene/sobol.tables"
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void sobol_generate_direction_vectors(uint vectors[][SOBOL_BITS], int dimensions)
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{
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assert(dimensions <= SOBOL_MAX_DIMENSIONS);
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const uint L = SOBOL_BITS;
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/* first dimension is exception */
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uint *v = vectors[0];
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for (uint i = 0; i < L; i++)
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v[i] = 1 << (31 - i); // all m's = 1
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for (int dim = 1; dim < dimensions; dim++) {
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const SobolDirectionNumbers *numbers = &SOBOL_NUMBERS[dim - 1];
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const uint s = numbers->s;
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const uint a = numbers->a;
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const uint *m = numbers->m;
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v = vectors[dim];
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if (L <= s) {
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for (uint i = 0; i < L; i++)
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v[i] = m[i] << (31 - i);
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}
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else {
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for (uint i = 0; i < s; i++)
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v[i] = m[i] << (31 - i);
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for (uint i = s; i < L; i++) {
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v[i] = v[i - s] ^ (v[i - s] >> s);
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for (uint k = 1; k < s; k++)
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v[i] ^= (((a >> (s - 1 - k)) & 1) * v[i - k]);
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}
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}
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}
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}
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CCL_NAMESPACE_END
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