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- /*
- * Implement Heap sort -- direct and indirect sorting
- * Based on descriptions in Sedgewick "Algorithms in C"
- * Copyright (C) 1999 Thomas Walter
- *
- * 18 February 2000: Modified for GSL by Brian Gough
- *
- * This is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the
- * Free Software Foundation; either version 3, or (at your option) any
- * later version.
- *
- * This source 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. See the GNU General Public License
- * for more details.
- */
- #include "gsl__config.h"
- #include <stdlib.h>
- #include "gsl_heapsort.h"
- static inline void downheap (size_t * p, const void *data, const size_t size, const size_t N, size_t k, gsl_comparison_fn_t compare);
- #define CMP(data,size,j,k) (compare((const char *)(data) + (size) * (j), (const char *)(data) + (size) * (k)))
- static inline void
- downheap (size_t * p, const void *data, const size_t size, const size_t N, size_t k, gsl_comparison_fn_t compare)
- {
- const size_t pki = p[k];
- while (k <= N / 2)
- {
- size_t j = 2 * k;
- if (j < N && CMP (data, size, p[j], p[j + 1]) < 0)
- {
- j++;
- }
- if (CMP (data, size, pki, p[j]) >= 0)
- {
- break;
- }
- p[k] = p[j];
- k = j;
- }
- p[k] = pki;
- }
- int
- gsl_heapsort_index (size_t * p, const void *data, size_t count, size_t size, gsl_comparison_fn_t compare)
- {
- /* Sort the array in ascending order. This is a true inplace
- algorithm with N log N operations. Worst case (an already sorted
- array) is something like 20% slower */
- size_t i, k, N;
- if (count == 0)
- {
- return GSL_SUCCESS; /* No data to sort */
- }
- for (i = 0; i < count; i++)
- {
- p[i] = i ; /* set permutation to identity */
- }
- /* We have n_data elements, last element is at 'n_data-1', first at
- '0' Set N to the last element number. */
- N = count - 1;
- k = N / 2;
- k++; /* Compensate the first use of 'k--' */
- do
- {
- k--;
- downheap (p, data, size, N, k, compare);
- }
- while (k > 0);
- while (N > 0)
- {
- /* first swap the elements */
- size_t tmp = p[0];
- p[0] = p[N];
- p[N] = tmp;
- /* then process the heap */
- N--;
- downheap (p, data, size, N, 0, compare);
- }
- return GSL_SUCCESS;
- }
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