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Diffstat (limited to 'isisd/topology/random.c')
| -rw-r--r-- | isisd/topology/random.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/isisd/topology/random.c b/isisd/topology/random.c new file mode 100644 index 00000000..d4ef9950 --- /dev/null +++ b/isisd/topology/random.c @@ -0,0 +1,154 @@ +/*********************************************************************/ +/* */ +/* current processor time in seconds */ +/* difference between two calls is processor time spent by your code */ +/* needs: <sys/types.h>, <sys/times.h> */ +/* depends on compiler and OS */ +/* */ +/*********************************************************************/ + +#include <sys/types.h> +#include <sys/times.h> + +float timer() + { struct tms hold; + + times(&hold); + return (float)(hold.tms_utime) / 60.0; + } + + +/*********************************************************************/ +/* */ +/* Family of random number generators */ +/* */ +/* Initialisation: */ +/* void init_rand ( seed ); */ +/* long seed - any positive number */ +/* if seed<=0 init_rand takes time */ +/* from timer instead of seed */ +/* */ +/* Whole number uniformly distributed on [0,n): */ +/* long nrand (n); */ +/* long n */ +/* */ +/* Real number uniformly distributed on [0,1] */ +/* double rand01(); */ +/* */ +/* Real number with Gauss(0,1) disitribution: */ +/* double randg01(); */ +/* */ +/* Algorithm: */ +/* x(n+1) = (x(n) * 5^13) mod 2^31 */ +/* */ +/*********************************************************************/ + +unsigned long internal_seed; + +void init_rand ( init_seed ) + +long init_seed; + +{ internal_seed = ( init_seed > 0 ) + ? (unsigned long) init_seed + : (unsigned long) timer(); + + + /* only odd numbers are acceptable */ + if ( internal_seed % 2 == 0 ) internal_seed --; +} + +/*********************************************************************/ +/* */ +/* Internal function irand may depend on OS and compiler */ +/* */ +/* irand assumption: */ +/* unsigned long i,j; */ +/* if i*j > max(unsigned long) */ +/* 1. No overflow interruption */ +/* 2. i*j = i*j mod max(unsigned long) */ +/* */ +/* This assumption is true for a lot of computers. */ +/* If your computer fails: */ +/* rename: irand <---> xrand */ +/* */ +/*********************************************************************/ + +#define A 1220703125 +#define B 2147483647 +#define BF 2147483647. + +static long irand () + +{ internal_seed = ( internal_seed * A ) & B; + return (long) internal_seed ; +} + +/*********************************************************************/ +/* */ +/* computer independent variant of irand */ +/* */ +/*********************************************************************/ + + +#define T15 32768 +#define T16 65536 +#define A1 37252 +#define A2 29589 + +static long xrand() + +{ unsigned long is1, is2; + + is1 = internal_seed / T15; + is2 = internal_seed % T15; + + internal_seed = ( (((is2 * A1) + (is1 * A2))% T16 )* T15 + (is2 * A2) ) & B; + return (long) ( internal_seed ) ; +} + + +/*********************************************************************/ + + +double rand01() + +{ return (double) irand() / BF ; +} + +/*********************************************************************/ + +#define NK 12 + +double randg01() + +{ int i; + double sum = 0; + + for ( i = 0; i < NK; i++ ) sum += rand01(); + return sum - 6.; + + /* if NK != 12 then you must return (12/NK)*sum - (NK/2) */ +} + +#undef NK + + +/*********************************************************************/ + +long nrand ( n ) + +long n; + +{ return (long) ( rand01() * (double) n ); +} + +/*********************************************************************/ + +#undef A +#undef A1 +#undef A2 +#undef B +#undef BF +#undef T15 +#undef T16 |