src/gmxlib/gmx_sort.c

   1 /* -*- mode: c; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; c-file-style: "stroustrup"; -*-
   2  *
   3  *
   4  * This file is part of Gromacs        Copyright (c) 1991-2010
   5  * David van der Spoel, Erik Lindahl, Berk Hess, University of Groningen.
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version 2
  10  * of the License, or (at your option) any later version.
  11  *
  12  * To help us fund GROMACS development, we humbly ask that you cite
  13  * the research papers on the package. Check out http://www.gromacs.org
  14  *
  15  * And Hey:
  16  * Gnomes, ROck Monsters And Chili Sauce
  17  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 #include <config.h>
  21 #endif
  22
  23 #include <stdlib.h>
  24 #include "gmx_sort.h"
  25
  26
  27 static void
  28 qsort_swapfunc(void *        a,
  29                void *        b,
  30                size_t        n,
  31                int           swaptype)
  32 {
  33     int *  ia;
  34     int *  ib;
  35     int    itmp;
  36
  37     char *  ca;
  38     char *  cb;
  39     char    ctmp;
  40
  41     if (swaptype <= 1)
  42     {
  43         ia = (int *)a;
  44         ib = (int *)b;
  45         for( ; n > 0; ia += 1, ib += 1, n -= sizeof(int))
  46         {
  47             itmp      = *ia;
  48             *ia       = *ib;
  49             *ib       = itmp;
  50         }
  51     }
  52     else
  53     {
  54         ca = (char *)a;
  55         cb = (char *)b;
  56         for( ; n > 0; ca += 1, cb += 1, n -= 1)
  57         {
  58             ctmp       = *ca;
  59             *ca        = *cb;
  60             *cb        = ctmp;
  61         }
  62     }
  63 }
  64
  65
  66 static void *
  67 qsort_med3(void *        a,
  68            void *        b,
  69            void *        c,
  70            int          (*compar) (const void *a, const void *b))
  71 {
  72     if(compar(a,b) < 0)
  73     {
  74         if(compar(b,c) < 0)
  75             return b;
  76         else if(compar(a,c) < 0)
  77             return c;
  78         else
  79             return a;
  80     }
  81     else
  82     {
  83         if(compar(b,c) > 0)
  84             return b;
  85         else if(compar(a,c) > 0)
  86             return c;
  87         else
  88             return a;
  89     }
  90 }
  91
  92
  93 void
  94 gmx_qsort(void *           base,
  95           size_t           nmemb,
  96           size_t           size,
  97           int            (*compar)(const void *, const void *))
  98 {
  99 #define QSORT_EXCH(a, b, t) (t = a, a = b, b = t)
 100 #define QSORT_SWAP(a, b) swaptype != 0 ? qsort_swapfunc(a, b, size, swaptype) : \
 101                             (void)QSORT_EXCH(*(int *)(a), *(int *)(b), t)
 102
 103     char *pa, *pb, *pc, *pd, *pl, *pm, *pn, *pv, *cbase;
 104     int r, swaptype;
 105     int t, v;
 106     size_t s, st;
 107
 108     cbase = (char *)base;
 109
 110     swaptype = (size_t)(cbase - (char *)0) % sizeof(int) || size % sizeof(int) ? 2 : size == sizeof(int)? 0 : 1;
 111
 112     if (nmemb < 7)
 113     {
 114         /* Insertion sort on smallest arrays */
 115         for (pm = cbase + size; pm < cbase + nmemb*size; pm += size)
 116         {
 117             for (pl = pm; (pl > cbase) && compar((void *)(pl-size),(void *) pl) > 0; pl -= size)
 118             {
 119                 QSORT_SWAP(pl, pl-size);
 120             }
 121         }
 122         return;
 123     }
 124
 125     /* Small arrays, middle element */
 126     pm = cbase + (nmemb/2)*size;
 127
 128     if (nmemb > 7)
 129     {
 130         pl = cbase;
 131         pn = cbase + (nmemb-1)*size;
 132         if (nmemb > 40)
 133         {
 134             /* Big arrays, pseudomedian of 9 */
 135             s = (nmemb/8)*size;
 136             pl = (char *)qsort_med3((void *)pl, (void *)((size_t)pl+s), (void *)((size_t)pl+2*s), compar);
 137             pm = (char *)qsort_med3((void *)((size_t)pm-s), (void *)pm, (void *)((size_t)pm+s), compar);
 138             pn = (char *)qsort_med3((void *)((size_t)pn-2*s), (void *)((size_t)pn-s), (void *)pn, compar);
 139         }
 140         /* Mid-size, med of 3 */
 141         pm = (char *)qsort_med3((void *)pl, (void *)pm, (void *)pn, compar);
 142     }
 143
 144     /* pv points to partition value */
 145     if (swaptype != 0)
 146     {
 147         pv = cbase;
 148         QSORT_SWAP(pv, pm);
 149     }
 150     else
 151     {
 152         pv = (char*)(void*)&v;
 153         v = *(int *)pm;
 154     }
 155
 156     pa = pb = cbase;
 157     pc = pd = cbase + (nmemb-1)*size;
 158
 159     for (;;)
 160     {
 161         while (pb <= pc && (r = compar((void *)pb,(void *) pv)) <= 0)
 162         {
 163             if (r == 0)
 164             {
 165                 QSORT_SWAP(pa, pb);
 166                 pa += size;
 167             }
 168             pb += size;
 169         }
 170         while (pc >= pb && (r = compar((void *)pc,(void *) pv)) >= 0)
 171         {
 172             if (r == 0)
 173             {
 174                 QSORT_SWAP(pc, pd);
 175                 pd -= size;
 176             }
 177             pc -= size;
 178         }
 179         if (pb > pc)
 180         {
 181             break;
 182         }
 183         QSORT_SWAP(pb, pc);
 184         pb += size;
 185         pc -= size;
 186     }
 187     pn = cbase + nmemb*size;
 188
 189     s  = pa-cbase;
 190     st = pb-pa;
 191     if(st<s)
 192     {
 193         s = st;
 194     }
 195
 196     if(s>0)
 197     {
 198         qsort_swapfunc(cbase, pb-s, s, swaptype);
 199     }
 200
 201     s = pd-pc;
 202     st = pn-pd-size;
 203     if(st<s)
 204     {
 205         s = st;
 206     }
 207
 208     if(s>0)
 209     {
 210         qsort_swapfunc(pb, pn-s, s, swaptype);
 211     }
 212
 213     if ((s = pb-pa) > size)
 214     {
 215         gmx_qsort(cbase, s/size, size, compar);
 216     }
 217
 218     if ((s = pd-pc) > size)
 219     {
 220         gmx_qsort(pn-s, s/size, size, compar);
 221     }
 222
 223 #undef QSORT_EXCH
 224 #undef QSORT_SWAP
 225
 226     return;
 227 }
 228
 229
 230