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// Copyright (c) 2021, Viktor Larsson
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// * Neither the name of the copyright holder nor the
// names of its contributors may be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
// ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "sampling.h"
#include <cmath>
namespace poselib {
// Splitmix64 PRNG
typedef uint64_t RNG_t;
int random_int(RNG_t &state) {
state += 0x9e3779b97f4a7c15;
uint64_t z = state;
z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
return z ^ (z >> 31);
}
// Draws a random sample
void draw_sample(size_t sample_sz, size_t N, std::vector<size_t> *sample, RNG_t &rng) {
for (size_t i = 0; i < sample_sz; ++i) {
bool done = false;
while (!done) {
(*sample)[i] = random_int(rng) % N;
done = true;
for (size_t j = 0; j < i; ++j) {
if ((*sample)[i] == (*sample)[j]) {
done = false;
break;
}
}
}
}
}
// Sampling for multi-camera systems
void draw_sample(size_t sample_sz, const std::vector<size_t> &N, std::vector<std::pair<size_t, size_t>> *sample,
RNG_t &rng) {
for (size_t i = 0; i < sample_sz; ++i) {
bool done = false;
while (!done) {
(*sample)[i].first = random_int(rng) % N.size();
if (N[(*sample)[i].first] == 0) {
continue;
}
(*sample)[i].second = random_int(rng) % N[(*sample)[i].first];
done = true;
for (size_t j = 0; j < i; ++j) {
if ((*sample)[i] == (*sample)[j]) {
done = false;
break;
}
}
}
}
}
void RandomSampler::generate_sample(std::vector<size_t> *sample) {
if (use_prosac && sample_k < max_prosac_iterations) {
draw_sample(sample_sz - 1, subset_sz - 1, sample, state);
(*sample)[sample_sz - 1] = subset_sz - 1;
// update prosac state
sample_k++;
if (sample_k < max_prosac_iterations) {
if (sample_k > growth[subset_sz - 1]) {
if (++subset_sz > num_data) {
subset_sz = num_data;
}
}
}
} else {
// uniform ransac sampling
draw_sample(sample_sz, num_data, sample, state);
}
}
void RandomSampler::initialize_prosac() {
growth.resize(std::max(num_data, sample_sz), 0);
// In the paper, T_N = max_prosac_iterations
// Initialize T_n for n = sample_sz
double T_n = max_prosac_iterations;
for (size_t i = 0; i < sample_sz; ++i)
T_n *= static_cast<double>(sample_sz - i) / (num_data - i);
// Note that that growth[] stores T_n prime
// The growth function is then defined as
// g(t) = smallest n such that T_n prime > t
for (size_t n = 0; n < sample_sz; ++n) {
growth[n] = 1;
}
size_t T_np = 1;
for (size_t n = sample_sz; n < num_data; ++n) {
// Recursive relation from eq. 3
double T_n_next = T_n * (n + 1.0) / (n + 1.0 - sample_sz);
// Eq. 4
T_np += std::ceil(T_n_next - T_n);
growth[n] = T_np;
T_n = T_n_next;
}
// counter keeping track of which sample we are at
sample_k = 1;
subset_sz = sample_sz;
}
} // namespace poselib
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