@xint main()@yint main(int argc, char **argv);int main(int argc, char **argv)@z@x  if (gb_unif_rand(0x55555555L)!=748103812) {     fprintf(stderr,"Failure on the second try!\n"); return -2;  }  fprintf(stderr,"OK, the gb_flip routines seem to work!\n");  return 0;@y  if (gb_unif_rand(0x55555555L)!=748103812) {     fprintf(stderr,"Failure on the second try!\n"); return -2;  }  @<Test the object-oriented generators@>@;  fprintf(stderr,"OK, the gb_flip routines seem to work!\n");  return 0;@z@x#define gb_next_rand() @t\quad@>(*gb_fptr>=0?*gb_fptr--:gb_flip_cycle())@y#ifndef gb_next_rand#define gb_next_rand() @t\quad@>(*gb_fptr>=0?*gb_fptr--:gb_flip_cycle())#endif@z@xextern long gb_flip_cycle(); /* compute 55 more pseudo-random numbers */@yextern long gb_flip_cycle(void); /* compute 55 more pseudo-random numbers */@z@xlong gb_flip_cycle()@ylong gb_flip_cycle(void);long gb_flip_cycle(void)@z@xvoid gb_init_rand(seed)    long seed;@yvoid gb_init_rand(long seed);void gb_init_rand(long seed)@z@xextern void gb_init_rand();@yextern void gb_init_rand(long seed);@z@xlong gb_unif_rand(m)    long m;@ylong gb_unif_rand(long m);long gb_unif_rand(long m)@z@xextern long gb_unif_rand();@yextern long gb_unif_rand(long m);@*Multiple independent streams.({\sl David Neto here.})Sometimes it is convenient to have multiple random number sequences aliveat once, especially when trying to tame a particularly obstreperous set of experiments.  Each generator is a separate object.I've just copied the code from above.  Alas, this not the easiestto maintain, but it works.  In any case, Knuth's code will never change, right?  Right?! (Insert smileys$\ldots$)To separate the namespace from Knuth'sroutines, each procedure or function name hasthe prefix |gb_prng|.These are compatible extensions to the Stanford GraphBase.  They are{\it not\/} part of the Stanford GraphBase.@(gb_flip.h@>=#define gb_prng_next_rand(PRNG) @t\quad@>(*(PRNG)->fptr>=0? *(PRNG)->fptr--: gb_prng_cycle((PRNG)))typedef struct {long *fptr;long A[56];} gb_prng_t;gb_prng_t *gb_prng_new(long seed);long gb_prng_cycle(gb_prng_t *prng);long gb_prng_unif_rand(gb_prng_t *prng, long m);void gb_prng_free(gb_prng_t *prng);@  Function |gb_prng_new| allocates and initializes the generator.@<External functions@>=#include <stdlib.h> /* We need |malloc|. */#include "gb_flip.h"gb_prng_t *gb_prng_new(long seed);gb_prng_t *gb_prng_new(long seed){	gb_prng_t *prng = malloc(sizeof(gb_prng_t));	if ( prng ) {		register long i;		register long prev=seed, next=1;		prng->A[0]=-1;		seed=prev=mod_diff(prev,0); /* strip off the sign */		prng->A[55]=prev;		for (i=21; i; i=(i+21)%55) {			prng->A[i]=next;			@<Compute a new |next| value, based on |next|, |prev|, and |seed|@>;			prev=prng->A[i];		}		gb_prng_cycle(prng);		gb_prng_cycle(prng);		gb_prng_cycle(prng);		gb_prng_cycle(prng);		gb_prng_cycle(prng);	}	return prng;}@ The other \CEE/ code is pretty easy if you've digested Knuth's code.@<External functions@>=long gb_prng_cycle(gb_prng_t *prng);long gb_prng_cycle(gb_prng_t *prng){@+register long *ii, *jj;  for (ii=&prng->A[1],jj=&prng->A[32];jj<=&prng->A[55];ii++,jj++)    *ii=mod_diff(*ii,*jj);  for (jj=&prng->A[1];ii<=&prng->A[55];ii++,jj++)    *ii=mod_diff(*ii,*jj);  prng->fptr=&prng->A[54];  return prng->A[55];}@@<External f...@>=long gb_prng_unif_rand(gb_prng_t *prng, long m);long gb_prng_unif_rand(gb_prng_t *prng, long m){@+register unsigned long t=two_to_the_31-(two_to_the_31 % m);  register long r;  do@+{    r=gb_prng_next_rand(prng);  }@+while (t<=(unsigned long)r);  return r%m;}@ Finally, we also add functionality for freeing the generator object.@<External f...@>=void gb_prng_free(gb_prng_t *prng) {	if ( prng ) {free(prng);}}@@<Test the object-oriented generators@>={ gb_prng_t *a, *b;    gb_init_rand(-314159L);  a=gb_prng_new(-314159L);  b=gb_prng_new(-314159L);  if (gb_next_rand()!=119318998  || gb_prng_next_rand(a)!=119318998  || gb_prng_next_rand(b)!=119318998) {     fprintf(stderr,"OO Failure on the first try!\n"); return -1;  }  for (j=1; j<=133; j++) {    gb_next_rand();    gb_prng_next_rand(a);    gb_prng_next_rand(b);  }  if ( gb_unif_rand(0x55555555L)!=748103812  || gb_prng_unif_rand(a,0x55555555L)!=748103812  || gb_prng_unif_rand(b,0x55555555L)!=748103812) {     fprintf(stderr,"OO Failure on the second try!\n"); return -2;  }  gb_prng_free(a);	  gb_prng_free(b);	}@z