wehub-resource-sync
41 lines
1.1 KiB
C
41 lines
1.1 KiB
C
/*
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Implements a simple Sampler, used during model inference to sample tokens.
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*/
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#ifndef SAMPLER_H
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#define SAMPLER_H
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#include <math.h>
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// Simple xorshift RNG
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unsigned int random_u32(unsigned long long *state) {
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// xorshift rng: https://en.wikipedia.org/wiki/Xorshift#xorshift.2A
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*state ^= *state >> 12;
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*state ^= *state << 25;
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*state ^= *state >> 27;
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return (*state * 0x2545F4914F6CDD1Dull) >> 32;
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}
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float random_f32(unsigned long long *state) { // random float32 in [0,1)
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return (random_u32(state) >> 8) / 16777216.0f;
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}
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int sample_softmax(const float* logits, int n, float coin) {
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// sample index from logits (converted to probabilities using softmax)
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// coin is a random number in [0, 1), usually from random_f32()
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double norm = 0;
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for (int i = 0; i < n; i++) {
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norm += expf(logits[i]);
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}
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// instead of dividing all exp(logits), we can just multiply coin.
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coin *= norm;
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float cdf = 0.0f;
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for (int i = 0; i < n; i++) {
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cdf += expf(logits[i]);
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if (coin < cdf) {
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return i;
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}
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}
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return n - 1; // in case of rounding errors
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}
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#endif |