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// 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 ETH Zurich and UNC Chapel Hill 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 THE 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.
//
// Author: Johannes L. Schoenberger (jsch-at-demuc-dot-de)
#include "optim/combination_sampler.h"
#include <numeric>
#include "util/math.h"
#include "util/random.h"
namespace colmap {
CombinationSampler::CombinationSampler(const size_t num_samples)
: num_samples_(num_samples) {}
void CombinationSampler::Initialize(const size_t total_num_samples) {
CHECK_LE(num_samples_, total_num_samples);
total_sample_idxs_.resize(total_num_samples);
// Note that the samples must be in increasing order for `NextCombination`.
std::iota(total_sample_idxs_.begin(), total_sample_idxs_.end(), 0);
}
size_t CombinationSampler::MaxNumSamples() {
return NChooseK(total_sample_idxs_.size(), num_samples_);
}
std::vector<size_t> CombinationSampler::Sample() {
std::vector<size_t> sampled_idxs(num_samples_);
for (size_t i = 0; i < num_samples_; ++i) {
sampled_idxs[i] = total_sample_idxs_[i];
}
if (!NextCombination(total_sample_idxs_.begin(),
total_sample_idxs_.begin() + num_samples_,
total_sample_idxs_.end())) {
// Reached all possible combinations, so reset to original state.
// Note that the samples must be in increasing order for `NextCombination`.
std::iota(total_sample_idxs_.begin(), total_sample_idxs_.end(), 0);
}
return sampled_idxs;
}
} // namespace colmap
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