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41 lines
1.5 KiB
C
41 lines
1.5 KiB
C
/*
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* PCG Random Number Generation for C.
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*
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* Copyright 2014 Melissa O'Neill <oneill@pcg-random.org>
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* For additional information about the PCG random number generation scheme,
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* including its license and other licensing options, visit
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*
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* http://www.pcg-random.org
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*/
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#include "pcg_basic.h"
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void pcg32_srandom_r(pcg32_random_t* rng, uint64_t initial_state, uint64_t initseq) {
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rng->state = 0U;
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rng->inc = (initseq << 1u) | 1u;
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pcg32_random_r(rng);
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rng->state += initial_state;
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pcg32_random_r(rng);
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}
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uint32_t pcg32_random_r(pcg32_random_t* rng) {
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uint64_t oldstate = rng->state;
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rng->state = oldstate * 6364136223846793005ULL + rng->inc;
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uint32_t xorshifted = (uint32_t)(((oldstate >> 18u) ^ oldstate) >> 27u);
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uint32_t rot = (uint32_t)(oldstate >> 59u);
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return (xorshifted >> rot) | (xorshifted << ((~rot + 1u) & 31)); /* was (xorshifted >> rot) | (xorshifted << ((-rot) & 31)) */
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}
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