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// Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
// Copyright (C) 1998-2003 Fast Search & Transfer ASA
// Copyright (C) 2003 Overture Services Norway AS
#pragma once
#include <algorithm>
#include <vespa/searchlib/util/inline.h>
namespace search {
/* Various sorting-related functions */
template <typename T, typename Compare>
inline always_inline__ T *
median3(T *a, T *b, T *c, Compare *compobj)
{
return Compare::Compare(compobj, *a, *b) < 0 ?
(Compare::Compare(compobj, *b, *c) < 0 ? b : Compare::Compare(compobj, *a, *c) < 0 ? c : a) :
(Compare::Compare(compobj, *b, *c) > 0 ? b : Compare::Compare(compobj, *a, *c) > 0 ? c : a);
}
template <typename T, typename Compare>
void
insertion_sort(T a[], unsigned int n, Compare *compobj)
{
unsigned int i, j;
T _swap;
for (i=1; i<n ; i++)
{
_swap = a[i];
j = i;
while (Compare::Compare(compobj, _swap, a[j-1]) < 0)
{
a[j] = a[j-1];
if(!(--j)) break;
}
a[j] = _swap;
}
}
template <int InsertSortLevel, int Median9Level, typename T,
typename Compare>
void
qsort(T *a, unsigned int n, Compare *compobj)
{
for (;;) {
if (n < InsertSortLevel) {
insertion_sort<T, Compare>(a, n, compobj);
return;
}
T *middle = a + (n/2);
T *left = a;
T *right = a + n - 1;
if (n > Median9Level) {
size_t s = n/8;
left = median3<T, Compare>
(left, left + s, left + 2*s, compobj);
middle = median3<T, Compare>
(middle - s, middle, middle+s, compobj);
right = median3<T, Compare>
(right - 2*s, right - s, right, compobj);
}
middle = median3<T, Compare>(left, middle, right, compobj);
T *pa, *pb, *pc, *pd;
pa = pb = a;
pc = pd = a + n - 1;
T swap;
T pivot = *middle;
int r;
for (;;) {
while (pb <= pc && (r = Compare::Compare(compobj, *pb, pivot)) <= 0) {
if (r == 0) {
swap = *pa;
*pa = *pb;
*pb = swap;
pa++;
}
pb++;
}
while (pb <= pc && (r = Compare::Compare(compobj, *pc, pivot)) >= 0) {
if (r == 0) {
swap = *pc;
*pc = *pd;
*pd = swap;
pd--;
}
pc--;
}
if (pb > pc)
break;
swap = *pb;
*pb = *pc;
*pc = swap;
pb++;
pc--;
}
right = a + n;
int s = std::min(pa - a, pb - pa);
T *swapa = a;
T *swapb = pb-s;
T *swapaend = a + s;
while (swapa < swapaend) {
T tmp = *swapa;
*swapa++ = *swapb;
*swapb++ = tmp;
}
s = std::min(pd - pc, right - pd - 1);
swapa = pb;
swapb = right - s;
swapaend = pb + s;
while (swapa < swapaend) {
T tmp = *swapa;
*swapa++ = *swapb;
*swapb++ = tmp;
}
// Recurse on the smaller partition.
if (pb - pa < pd - pc) {
if ((s = pb - pa) > 1)
qsort<InsertSortLevel, Median9Level, T, Compare>
(a, s, compobj);
if ((s = pd - pc) > 1) {
a = right - s;
n = s;
continue;
}
} else {
if ((s = pd - pc) > 1)
qsort<InsertSortLevel, Median9Level, T, Compare>
(right - s, s, compobj);
if ((s = pb - pa) > 1) {
n = s;
continue;
}
}
break;
}
}
}
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