Diffstat (limited to 'noncore/games/sfcave-sdl/random.cpp') (more/less context) (ignore whitespace changes)
| -rw-r--r-- | noncore/games/sfcave-sdl/random.cpp | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/noncore/games/sfcave-sdl/random.cpp b/noncore/games/sfcave-sdl/random.cpp new file mode 100644 index 0000000..9f716f2 --- a/dev/null +++ b/noncore/games/sfcave-sdl/random.cpp @@ -0,0 +1,189 @@ +/* ------------------------------------------------------------------------- + * This is an ANSI C library for multi-stream random number generation. + * The use of this library is recommended as a replacement for the ANSI C + * rand() and srand() functions, particularly in simulation applications + * where the statistical 'goodness' of the random number generator is + * important. The library supplies 256 streams of random numbers; use + * SelectStream(s) to switch between streams indexed s = 0,1,...,255. + * + * The streams must be initialized. The recommended way to do this is by + * using the function PlantSeeds(x) with the value of x used to initialize + * the default stream and all other streams initialized automatically with + * values dependent on the value of x. The following convention is used + * to initialize the default stream: + * if x > 0 then x is the state + * if x < 0 then the state is obtained from the system clock + * if x = 0 then the state is to be supplied interactively. + * + * The generator used in this library is a so-called 'Lehmer random number + * generator' which returns a pseudo-random number uniformly distributed + * 0.0 and 1.0. The period is (m - 1) where m = 2,147,483,647 and the + * smallest and largest possible values are (1 / m) and 1 - (1 / m) + * respectively. For more details see: + * + * "Random Number Generators: Good Ones Are Hard To Find" + * Steve Park and Keith Miller + * Communications of the ACM, October 1988 + * + * Name : rngs.c (Random Number Generation - Multiple Streams) + * Authors : Steve Park & Dave Geyer + * Language : ANSI C + * Latest Revision : 09-22-98 + * ------------------------------------------------------------------------- + */ + +#include <stdio.h> +#include <time.h> + +#define __RANDOM_CPP +#include "random.h" + +#define MODULUS 2147483647 /* DON'T CHANGE THIS VALUE */ +#define MULTIPLIER 48271 /* DON'T CHANGE THIS VALUE */ +#define CHECK 399268537 /* DON'T CHANGE THIS VALUE */ +#define STREAMS 256 /* # of streams, DON'T CHANGE THIS VALUE */ +#define A256 22925 /* jump multiplier, DON'T CHANGE THIS VALUE */ +#define DEFAULT 123456789 /* initial seed, use 0 < DEFAULT < MODULUS */ + +static long seed[STREAMS] = {DEFAULT}; /* current state of each stream */ +static int stream = 0; /* stream index, 0 is the default */ +static int initialized = 0; /* test for stream initialization */ + + + double Random(void) +/* ---------------------------------------------------------------- + * Random returns a pseudo-random real number uniformly distributed + * between 0.0 and 1.0. + * ---------------------------------------------------------------- + */ +{ + const long Q = MODULUS / MULTIPLIER; + const long R = MODULUS % MULTIPLIER; + long t; + + t = MULTIPLIER * (seed[stream] % Q) - R * (seed[stream] / Q); + if (t > 0) + seed[stream] = t; + else + seed[stream] = t + MODULUS; + return ((double) seed[stream] / MODULUS); +} + + + void PlantSeeds(long x) +/* --------------------------------------------------------------------- + * Use this function to set the state of all the random number generator + * streams by "planting" a sequence of states (seeds), one per stream, + * with all states dictated by the state of the default stream. + * The sequence of planted states is separated one from the next by + * 8,367,782 calls to Random(). + * --------------------------------------------------------------------- + */ +{ + const long Q = MODULUS / A256; + const long R = MODULUS % A256; + int j; + int s; + + initialized = 1; + s = stream; /* remember the current stream */ + SelectStream(0); /* change to stream 0 */ + PutSeed(x); /* set seed[0] */ + stream = s; /* reset the current stream */ + for (j = 1; j < STREAMS; j++) { + x = A256 * (seed[j - 1] % Q) - R * (seed[j - 1] / Q); + if (x > 0) + seed[j] = x; + else + seed[j] = x + MODULUS; + } +} + + +int nextInteger( int range,const char *file, int line ) +{ + int val = (int)(Random( ) * range); +// printf( "nextInt() called from %s line %d - returning %d\n", file, line, val ); + + return val; + +} + void PutSeed(long x) +/* --------------------------------------------------------------- + * Use this function to set the state of the current random number + * generator stream according to the following conventions: + * if x > 0 then x is the state (unless too large) + * if x < 0 then the state is obtained from the system clock + * if x = 0 then the state is to be supplied interactively + * --------------------------------------------------------------- + */ +{ + char ok = 0; + + if (x > 0) + x = x % MODULUS; /* correct if x is too large */ + if (x < 0) + x = ((unsigned long) time((time_t *) NULL)) % MODULUS; + if (x == 0) + while (!ok) { + printf("\nEnter a positive integer seed (9 digits or less) >> "); + scanf("%ld", &x); + ok = (0 < x) && (x < MODULUS); + if (!ok) + printf("\nInput out of range ... try again\n"); + } + seed[stream] = x; +} + + + void GetSeed(long *x) +/* --------------------------------------------------------------- + * Use this function to get the state of the current random number + * generator stream. + * --------------------------------------------------------------- + */ +{ + *x = seed[stream]; +} + + + void SelectStream(int index) +/* ------------------------------------------------------------------ + * Use this function to set the current random number generator + * stream -- that stream from which the next random number will come. + * ------------------------------------------------------------------ + */ +{ + stream = ((unsigned int) index) % STREAMS; + if ((initialized == 0) && (stream != 0)) /* protect against */ + PlantSeeds(DEFAULT); /* un-initialized streams */ +} + + + void TestRandom(void) +/* ------------------------------------------------------------------ + * Use this (optional) function to test for a correct implementation. + * ------------------------------------------------------------------ + */ +{ + long i; + long x; + double u; + char ok = 0; + + SelectStream(0); /* select the default stream */ + PutSeed(1); /* and set the state to 1 */ + for(i = 0; i < 10000; i++) + u = Random(); + GetSeed(&x); /* get the new state value */ + ok = (x == CHECK); /* and check for correctness */ + + SelectStream(1); /* select stream 1 */ + PlantSeeds(1); /* set the state of all streams */ + GetSeed(&x); /* get the state of stream 1 */ + ok = ok && (x == A256); /* x should be the jump multiplier */ + if (ok) + printf("\n The implementation of rngs.c is correct.\n\n"); + else + printf("\n\a ERROR -- the implementation of rngs.c is not correct.\n\n"); +} |