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misc.cpp
/*
* Copyright (C) 2015-2020 Mateusz Łącki and Michał Startek.
*
* This file is part of IsoSpec.
*
* IsoSpec is free software: you can redistribute it and/or modify
* it under the terms of the Simplified ("2-clause") BSD licence.
*
* IsoSpec is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*
* You should have received a copy of the Simplified BSD Licence
* along with IsoSpec. If not, see <https://opensource.org/licenses/BSD-2-Clause>.
*/
#include "misc.h"
#include <utility>
#include "platform.h"
#include "isoMath.h"
namespace IsoSpec
{
void* quickselect(void ** array, size_t n, size_t start, size_t end)
{
if(start == end)
return array[start];
while(true)
{
// Partition part
size_t len = end - start;
#if ISOSPEC_BUILDING_R
size_t pivot = len/2 + start;
#else
size_t pivot = random_gen() % len + start; // Using Mersenne twister directly - we don't
// need a very uniform distribution just for pivot
// selection
#endif
void* pval = array[pivot];
double pprob = getLProb(pval);
std::swap(array[pivot], array[end-1]);
size_t loweridx = start;
for(size_t i = start; i < end-1; i++)
{
if(getLProb(array[i]) < pprob)
{
std::swap(array[i], array[loweridx]);
loweridx++;
}
}
std::swap(array[end-1], array[loweridx]);
// Selection part
if(n == loweridx)
return array[n];
if(n < loweridx)
end = loweridx;
else
start = loweridx+1;
};
}
} // namespace IsoSpec
IsoSpec
Definition allocator.cpp:21