foundationdb/fdbrpc/ContinuousSample.h

98 lines
2.3 KiB
C++

/*
* ContinuousSample.h
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef CONTINUOUSSAMPLE_H
#define CONTINUOUSSAMPLE_H
#pragma once
#include "flow/Platform.h"
#include "flow/IRandom.h"
#include <vector>
#include <algorithm>
#include <cmath>
template <class T>
class ContinuousSample {
public:
explicit ContinuousSample( int sampleSize ) : sampleSize( sampleSize ), populationSize( 0 ), sorted( true ), _min(T()), _max(T()) {}
ContinuousSample<T>& addSample(T sample) {
if( !populationSize )
_min = _max = sample;
populationSize++;
sorted = false;
if( populationSize <= sampleSize ) {
samples.push_back( sample );
} else if( g_random->random01() < ( (double)sampleSize / populationSize ) ) {
samples[ g_random->randomInt( 0, sampleSize ) ] = sample;
}
_max = std::max( _max, sample );
_min = std::min( _min, sample );
return *this;
}
double mean() {
if (!samples.size()) return 0;
T sum = 0;
for( int c = 0; c < samples.size(); c++ )
sum += samples[ c ];
return (double)sum / samples.size();
}
T median() {
return percentile( 0.5 );
}
T percentile( double percentile ) {
if( !samples.size() || percentile < 0.0 || percentile > 1.0 )
return T();
sort();
int idx = std::floor( ( samples.size() - 1 ) * percentile );
return samples[ idx ];
}
T min() { return _min; }
T max() { return _max; }
void clear() {
samples.clear();
populationSize = 0;
sorted = true;
_min = _max = 0; // Doesn't work for all T
}
private:
int sampleSize;
uint64_t populationSize;
bool sorted;
std::vector<T> samples;
T _min, _max;
void sort() {
if( !sorted && samples.size() > 1 )
std::sort( samples.begin(), samples.end() );
sorted = true;
}
};
#endif