Blame - isisd/topology/random.c - quagga

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jardin	eb5d44e	2003-12-23 08:09:43 +0000	[diff] [blame]	1	/*********************************************************************/
				2	/* */
				3	/* current processor time in seconds */
				4	/* difference between two calls is processor time spent by your code */
				5	/* needs: <sys/types.h>, <sys/times.h> */
				6	/* depends on compiler and OS */
				7	/* */
				8	/*********************************************************************/
				9
				10	#include <sys/types.h>
				11	#include <sys/times.h>
				12
hasso	29e50b2	2005-09-01 18:18:47 +0000	[diff] [blame]	13	unsigned long timer()
jardin	eb5d44e	2003-12-23 08:09:43 +0000	[diff] [blame]	14	{ struct tms hold;
				15
				16	times(&hold);
hasso	29e50b2	2005-09-01 18:18:47 +0000	[diff] [blame]	17	return (unsigned long) ((float) (hold.tms_utime) / 60.0);
jardin	eb5d44e	2003-12-23 08:09:43 +0000	[diff] [blame]	18	}
				19
				20
				21	/*********************************************************************/
				22	/* */
				23	/* Family of random number generators */
				24	/* */
				25	/* Initialisation: */
				26	/* void init_rand ( seed ); */
				27	/* long seed - any positive number */
				28	/* if seed<=0 init_rand takes time */
				29	/* from timer instead of seed */
				30	/* */
				31	/* Whole number uniformly distributed on [0,n): */
				32	/* long nrand (n); */
				33	/* long n */
				34	/* */
				35	/* Real number uniformly distributed on [0,1] */
				36	/* double rand01(); */
				37	/* */
				38	/* Real number with Gauss(0,1) disitribution: */
				39	/* double randg01(); */
				40	/* */
				41	/* Algorithm: */
				42	/* x(n+1) = (x(n) * 5^13) mod 2^31 */
				43	/* */
				44	/*********************************************************************/
				45
				46	unsigned long internal_seed;
				47
				48	void init_rand ( init_seed )
				49
				50	long init_seed;
				51
				52	{ internal_seed = ( init_seed > 0 )
				53	? (unsigned long) init_seed
				54	: (unsigned long) timer();
				55
				56
				57	/* only odd numbers are acceptable */
				58	if ( internal_seed % 2 == 0 ) internal_seed --;
				59	}
				60
				61	/*********************************************************************/
				62	/* */
				63	/* Internal function irand may depend on OS and compiler */
				64	/* */
				65	/* irand assumption: */
				66	/* unsigned long i,j; */
				67	/* if ij > max(unsigned long) /
				68	/* 1. No overflow interruption */
				69	/* 2. ij = ij mod max(unsigned long) */
				70	/* */
				71	/* This assumption is true for a lot of computers. */
				72	/* If your computer fails: */
				73	/* rename: irand <---> xrand */
				74	/* */
				75	/*********************************************************************/
				76
				77	#define A 1220703125
				78	#define B 2147483647
				79	#define BF 2147483647.
				80
				81	static long irand ()
				82
				83	{ internal_seed = ( internal_seed * A ) & B;
				84	return (long) internal_seed ;
				85	}
				86
hasso	29e50b2	2005-09-01 18:18:47 +0000	[diff] [blame]	87	#if 0 /* Not used. */
jardin	eb5d44e	2003-12-23 08:09:43 +0000	[diff] [blame]	88	/*********************************************************************/
				89	/* */
				90	/* computer independent variant of irand */
				91	/* */
				92	/*********************************************************************/
				93
				94
				95	#define T15 32768
				96	#define T16 65536
				97	#define A1 37252
				98	#define A2 29589
				99
				100	static long xrand()
				101
				102	{ unsigned long is1, is2;
				103
				104	is1 = internal_seed / T15;
				105	is2 = internal_seed % T15;
				106
				107	internal_seed = ( (((is2 * A1) + (is1 * A2))% T16 )* T15 + (is2 * A2) ) & B;
				108	return (long) ( internal_seed ) ;
				109	}
hasso	29e50b2	2005-09-01 18:18:47 +0000	[diff] [blame]	110	#endif
jardin	eb5d44e	2003-12-23 08:09:43 +0000	[diff] [blame]	111
				112	/*********************************************************************/
				113
				114
				115	double rand01()
				116
hasso	29e50b2	2005-09-01 18:18:47 +0000	[diff] [blame]	117	{ return (double) (irand() / BF) ;
jardin	eb5d44e	2003-12-23 08:09:43 +0000	[diff] [blame]	118	}
				119
				120	/*********************************************************************/
				121
				122	#define NK 12
				123
				124	double randg01()
				125
				126	{ int i;
				127	double sum = 0;
				128
				129	for ( i = 0; i < NK; i++ ) sum += rand01();
				130	return sum - 6.;
				131
				132	/* if NK != 12 then you must return (12/NK)sum - (NK/2) /
				133	}
				134
				135	#undef NK
				136
				137
				138	/*********************************************************************/
				139
				140	long nrand ( n )
				141
				142	long n;
				143
				144	{ return (long) ( rand01() * (double) n );
				145	}
				146
				147	/*********************************************************************/
				148
				149	#undef A
				150	#undef A1
				151	#undef A2
				152	#undef B
				153	#undef BF
				154	#undef T15
				155	#undef T16