189 lines
3.8 KiB
Plaintext
189 lines
3.8 KiB
Plaintext
/* DISTRIB.C - Procedures for handling distributions over numbers. */
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/* Copyright (c) 1995-2012 by Radford M. Neal and Peter Junteng Liu.
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*
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* Permission is granted for anyone to copy, use, modify, and distribute
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* these programs and accompanying documents for any purpose, provided
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* this copyright notice is retained and prominently displayed, and note
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* is made of any changes made to these programs. These programs and
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* documents are distributed without any warranty, express or implied.
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* As the programs were written for research purposes only, they have not
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* been tested to the degree that would be advisable in any important
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* application. All use of these programs is entirely at the user's own
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* risk.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <math.h>
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#include <string.h>
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#include "alloc.h"
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#include "distrib.h"
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/* CREATE A DISTRIBUTION AS SPECIFIED IN A STRING. Space for the distribution
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is allocated; the string is not freed.
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The string must consist either of a single positive integer, representing
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the distribution over just that number, or have a form such as the
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following:
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5x2/3.5x1/1.5x4
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This specifies a distribution over 3 numbers, 2, 1, and 4, specified by
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the second number in each pair, with proportions of 0.5, 0.35, and 0.15,
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respectively, specified by the first number in each pair. The actual
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proportions are found by dividing the first number in each pair by the sum
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of these numbers.
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The distrib type represents the distribution list. It stores a pointer to
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an array of distrib_entry elements along with the length of this array.
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Each distrib_entry contains a (number,proportion) pair.
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*/
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distrib *distrib_create
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( char *c /* String describing distribution over numbers */
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)
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{
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distrib *d;
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char *str, *tstr;
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int i, n, scan_num, size;
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double prop, sum;
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char junk;
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/* Check for special case of a single number. */
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if (sscanf(c,"%d%c",&n,&junk)==1 && n>0)
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{ tstr = chk_alloc ( (int)(4.1+log10(n)), sizeof(*tstr));
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sprintf(tstr,"1x%d",n);
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d = distrib_create(tstr);
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free(tstr);
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return d;
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}
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/* Initial scan of string for size and proper usage. */
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str = c;
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size = 0;
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sum = 0;
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d = chk_alloc(1, sizeof *d);
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for (;;)
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{
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scan_num = sscanf(str, "%lgx%d%c", &prop, &n, &junk);
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if ((scan_num!=2 && scan_num!=3) || prop<=0 || n<=0)
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{ return 0;
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}
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if (scan_num==3 && junk!='/')
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{ return 0;
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}
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size += 1;
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sum += prop;
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if (scan_num==2)
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{ break;
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}
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else
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{ str = (char*)strchr(str, '/') + 1;
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}
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}
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/* Allocate memory for the list and fill it in */
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d->size = size;
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d->list = chk_alloc (size, sizeof(distrib_entry));
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i = 0;
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str = c;
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for (;;)
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{
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scan_num = sscanf(str, "%lgx%d%c", &prop, &n, &junk);
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d->list[i].prop = prop/sum;
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d->list[i].num = n;
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i += 1;
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if (scan_num==2)
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{ break;
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}
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else if (scan_num==3)
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{ str = (char*)strchr(str, '/') + 1;
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}
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else
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{ abort();
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}
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}
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return d;
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}
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/* FREE SPACE OCCUPIED A DISTRIBUTION LIST. */
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void distrib_free
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( distrib *d /* List to free */
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)
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{ free(d->list);
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free(d);
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}
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/* RETURN THE MAXIMUM NUMBER IN A DISTRIBUTION LIST. Returns 0 if the list
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pointer is 0. */
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int distrib_max
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( distrib *d /* List to examine */
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)
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{
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int i;
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int cur;
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if (d==0) return 0;
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cur = 0;
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for (i = 1; i<d->size; i++)
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{ if (d->list[i].num > d->list[cur].num)
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{ cur = i;
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}
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}
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return d->list[cur].num;
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}
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/* TEST PROGRAM. */
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#ifdef TEST_DISTRIB
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main
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( int argc,
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char **argv
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)
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{
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distrib *d;
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int i, j;
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for (i = 1; i<argc; i++)
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{ d = distrib_create(argv[i]);
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if (d==0)
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{ printf("Error\n\n");
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}
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else
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{ for (j = 0; j<distrib_size(d); j++)
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{ printf("%.3f %d\n",distrib_prop(d,j),distrib_num(d,j));
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}
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printf("\n");
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}
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}
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exit(0);
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}
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#endif
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