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>2) close(random->logfd); // could be stdo/e
  59
  60         return 0;
  61 }
  62
  63 unsigned int rand_get(t_random *random) {
  64
  65         int left;
  66
  67         if(random->b_ptr==random->buffer+RAND_BUFSIZE) {
  68                 if(random->status&RAND_STAT_VERBOSE)
  69                         dprintf(random->logfd,
  70                                 "[random] getting new random numbers\n");
  71                 if(!(random->status&RAND_STAT_UDEV)) {
  72                         lseek(random->fd,0,SEEK_SET);
  73                         dprintf(random->logfd,
  74                                 "[random] warning, rereading random file\n");
  75                 }
  76                 left=RAND_BUFSIZE*sizeof(unsigned int);
  77                 while(left) {
  78                         left-=read(random->fd,
  79                                    random->buffer+\
  80                                    RAND_BUFSIZE*sizeof(unsigned int)-left,
  81                                    left);
  82                 }
  83                 if(random->status&RAND_STAT_VERBOSE)
  84                         dprintf(random->logfd,
  85                                 "[random] got new random numbers\n");
  86                 random->b_ptr=random->buffer;
  87         }
  88
  89         return(*(random->b_ptr++));
  90 }
  91
  92 double rand_get_double(t_random *random) {
  93
  94         return(1.0*rand_get(random)/((long long unsigned int)URAND_MAX+1));
  95 }
  96
  97 double rand_get_double_linear(t_random *random,double a,double b) {
  98
  99         return((-b+sqrt(b*b+2*a*(b+a/2)*rand_get_double(random)))/a);
 100 }
 101
 102 double rand_get_gauss(t_random *random) {
 103
 104         double a,b,w;
 105
 106         if(random->status&RAND_STAT_GAUSS) {
 107                 random->status&=~RAND_STAT_GAUSS;
 108                 return random->gauss;
 109         }
 110
 111         w=0;
 112         while((w>=1.0)||(w==0.0)) {
 113                 a=-2.0*rand_get_double(random)+1.0;
 114                 b=-2.0*rand_get_double(random)+1.0;
 115                 w=a*a+b*b;
 116         }
 117
 118         w=sqrt(-2.0*log(w)/w);
 119
 120         random->gauss=b*w;
 121         random->status|=RAND_STAT_GAUSS;
 122
 123         return(a*w);
 124 }
 125
 126 unsigned int rand_get_int_linear(t_random *random,unsigned int max,
 127                              double a,double b) {
 128
 129         return((int)(rand_get_double_linear(random,a,b)*max));
 130 }
 131
 132 unsigned int rand_get_reject(t_random *random,unsigned int max_x,
 133                              unsigned int max_y,unsigned int *graph) {
 134
 135         unsigned int x,y;
 136         unsigned char ok;
 137
 138         ok=0;
 139         while(!ok) {
 140                 x=(max_x*rand_get_double(random));
 141                 y=(max_y*rand_get_double(random));
 142                 if(y<=graph[x]) ok=1;
 143         }
 144
 145         return x;
 146 }
 147