35 lines
1021 B
C
35 lines
1021 B
C
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#include "pcg.h"
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// Random number generator.
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// Based on:
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// *Really* minimal PCG32 code / (c) 2014 M.E. O'Neill / pcg-random.org
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// Licensed under Apache License 2.0 (NO WARRANTY, etc. see website)
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uint64_t state = 0x853c49e6748fea9bULL;
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uint64_t inc = 0xda3e39cb94b95bdbULL;
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// Update seed of generator.
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void pcg_seed(uint64_t seed) {
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state = seed;
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}
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// Generate random integer.
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uint32_t pcg_rand() {
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uint64_t oldstate = state;
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// Advance internal state
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state = oldstate * 6364136223846793005ULL + (inc|1);
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// Calculate output function (XSH RR), uses old state for max ILP
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uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
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uint32_t rot = oldstate >> 59u;
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return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
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}
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// Fill out buffer with size random bytes.
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void pcg_bytes(char* out, int size) {
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// TODO: We can be more efficient by using all 4
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// pieces of the random number returned.
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for (int i = 0; i < size; i ++) {
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out[i] = (char)pcg_rand();
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}
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}
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