random/random.c

   1 /*
   2  * random.c - basic random deviates
   3  *
   4  * author: Frank Zirkelbach <frank.zirkelbach@physik.uni-augsburg.de>
   5  *
   6  */
   7
   8 #define _GNU_SOURCE
   9 #include <stdio.h>
  10 #include <sys/types.h>
  11 #include <sys/stat.h>
  12 #include <fcntl.h>
  13 #include <unistd.h>
  14 #include <stdlib.h>
  15 #include <math.h>
  16
  17 #include "random.h"
  18
  19 int rand_init(t_random *random,char *randomfile,int logfd) {
  20
  21         random->status=0;
  22
  23         if(logfd) random->logfd=logfd;
  24
  25         if(randomfile==NULL) {
  26                 random->fd=open("/dev/urandom",O_RDONLY);
  27                 if(random->fd<0) {
  28                         perror("open urandom");
  29                         return -1;
  30                 }
  31                 random->status|=RAND_STAT_UDEV;
  32         } else {
  33                 random->fd=open(randomfile,O_RDONLY);
  34                 if(random->fd<0) {
  35                         perror("open randomfile");
  36                         return -1;
  37                 }
  38         }
  39         random->buffer=malloc(RAND_BUFSIZE*sizeof(unsigned int));
  40         if(random->buffer==NULL) {
  41                 perror("malloc random buffer");
  42                 return -1;
  43         }
  44         random->b_ptr=random->buffer+RAND_BUFSIZE;
  45
  46         dprintf(random->logfd,"[random] init successfull\n");
  47
  48         return 0;
  49 }
  50
  51
  52 int rand_close(t_random *random) {
  53
  54         dprintf(random->logfd,"[random] shutdown\n");
  55
  56         if(random->buffer) free(random->buffer);
  57         if(random->fd) close(random->fd);
  58         if(random->logfd) close(random->logfd);
  59
  60         return 0;
  61 }
  62
  63 unsigned int rand_get(t_random *random) {
  64
  65         if(random->b_ptr==random->buffer+RAND_BUFSIZE) {
  66                 if(random->status&RAND_STAT_VERBOSE)
  67                         dprintf(random->logfd,
  68                                 "[random] getting new random numbers\n");
  69                 random->b_ptr=random->buffer;
  70                 if(!(random->status&RAND_STAT_UDEV)) {
  71                         lseek(random->fd,0,SEEK_SET);
  72                         dprintf(random->logfd,
  73                                 "[random] warning, rereading random file\n");
  74                 }
  75                 read(random->fd,random->b_ptr,
  76                      RAND_BUFSIZE*sizeof(unsigned int));
  77                 if(random->status&RAND_STAT_VERBOSE)
  78                         dprintf(random->logfd,
  79                                 "[random] got new random numbers\n");
  80         }
  81
  82         return(*(random->b_ptr++));
  83 }
  84
  85 double rand_get_double(t_random *random) {
  86
  87         return(1.0*rand_get(random)/(double)(URAND_MAX+1));
  88 }
  89
  90 double rand_get_double_linear(t_random *random,double a,double b) {
  91
  92         return((-b+sqrt(b*b+2*a*(b+a/2)*rand_get_double(random)))/a);
  93 }
  94
  95 double rand_get_gauss(t_random *random) {
  96
  97         double a,b,w;
  98
  99         if(random->status&RAND_STAT_GAUSS) {
 100                 random->status&=~RAND_STAT_GAUSS;
 101                 return random->gauss;
 102         }
 103
 104         w=0;
 105         while((w>=1.0)||(w==0.0)) {
 106                 a=-2.0*rand_get_double(random)+1.0;
 107                 b=-2.0*rand_get_double(random)+1.0;
 108                 w=a*a+b*b;
 109         }
 110
 111         w=sqrt(-2.0*log(w)/w);
 112
 113         random->gauss=b*w;
 114         random->status|=RAND_STAT_GAUSS;
 115
 116         return(a*w);
 117 }
 118
 119 unsigned int rand_get_int_linear(t_random *random,unsigned int max,
 120                              double a,double b) {
 121
 122         return((int)(rand_get_double_linear(random,a,b)*max));
 123 }
 124
 125 unsigned int rand_get_reject(t_random *random,unsigned int max_x,
 126                              unsigned int max_y,unsigned int *graph) {
 127
 128         unsigned int x,y;
 129         unsigned char ok;
 130
 131         ok=0;
 132         while(!ok) {
 133                 x=(max_x*rand_get_double(random));
 134                 y=(max_y*rand_get_double(random));
 135                 if(y<=graph[x]) ok=1;
 136         }
 137
 138         return x;
 139 }
 140