Function shuffle_samples

common/train.cpp:313–358

}

std::string shuffle_samples(
        const std::string & rng_state,
        size_t            * shuffled_offs,
        size_t            * shuffled_begins,
        size_t            * shuffled_sizes,
        const size_t      * begins,
        const size_t      * sizes,
        size_t              count) {
    if (count == 0) return rng_state;

    std::mt19937 rng;
    mt19937_set_state(rng, rng_state);

    // sort indices by random value for each index
    std::vector<size_t> idcs;
    {
        std::vector<unsigned> rnd;
        idcs.resize(count);
        rnd.resize(count);
        for (unsigned i=0; i<count; ++i) {
            idcs[i] = i;
            rnd[i]  = rng();
        }

        std::sort(idcs.begin(), idcs.end(), [&rnd](size_t a, size_t b){
            // stable sort for reproducibility
            return (rnd[a] == rnd[b]) ? (a < b) : (rnd[a] < rnd[b]);
        });
    }

    // create random offsets
    for (unsigned i=0; i<count; ++i) {
        shuffled_offs[i] = (size_t) ((sizes[idcs[i]] - 1) * ((double) rng() / (double) (rng.max()-1)));
    }

    // reorder begins and sizes by sorted indices
    for (unsigned i=0; i<count; ++i) {
        shuffled_begins[i] = begins[idcs[i]];
    }

    for (unsigned i=0; i<count; ++i) {
        shuffled_sizes[i] = sizes[idcs[i]];
    }

    return mt19937_get_state(rng);
}

size_t hash_combine(size_t h1, size_t h2) {
    return h1 ^ (h2 << 1);