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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <algorithm>
namespace proton::matching {
/**
* This class is used for all calculations related to limiting the
* number of results produced during matching based on the 'max-hits'
* configuration in the 'match-phase' part of the rank profile in the
* search definition.
**/
class MatchPhaseLimitCalculator
{
private:
const size_t _max_hits;
const size_t _min_groups;
const size_t _sample_hits;
public:
/**
* @param max_hits the number of hits you want
* @param min_groups the minimum number of diversity groups you want
* @param sample fraction of max_hits to be used as sample size before performing match phase limiting
*/
MatchPhaseLimitCalculator(size_t max_hits, size_t min_groups, double sample) :
_max_hits(max_hits),
_min_groups(std::max(size_t(1), min_groups)),
_sample_hits(max_hits * sample)
{}
size_t sample_hits_per_thread(size_t num_threads) const {
return std::max(size_t(1), std::max(128 / num_threads, _sample_hits / num_threads));
}
size_t wanted_num_docs(double hit_rate) const {
return std::min((double)0x7fffFFFF, std::max(128.0, _max_hits / hit_rate));
}
size_t estimated_hits(double hit_rate, size_t num_docs) const {
return (size_t) (hit_rate * num_docs);
}
size_t max_group_size(size_t wanted_num_docs_in) const {
return (wanted_num_docs_in / _min_groups);
}
};
}
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