# random(3f) [bsd man page]

RANDOM(3F) RANDOM(3F)NAME

random, drandm, irandm - better random number generatorSYNOPSIS

function irandm (iflag) function random (iflag) double precision function drandm (iflag)DESCRIPTION

These functions use random(3) to generate sequences of random numbers, and should be used rather than the older functions described in man 3f rand. If iflag is non-zero, it is used as a new seed for the random number generator, and the first new random value is returned. Irandm returns positive integers in the range 0 through 2147483647 ( 2**31-1). Random and drandm return values in the range 0. through 1.0 by dividing the integer random number from random(3) by 2147483647 .FILES

/usr/lib/libF77.aSEE ALSO

random(3)4.3 Berkeley DistributionMay 15, 1985 RANDOM(3F)

## Check Out this Related Man Page

RANDOM(3) Linux Programmer's Manual RANDOM(3)NAME

random, srandom, initstate, setstate - random number generator.SYNOPSIS

#include <stdlib.h> long int random(void); void srandom(unsigned int seed); char *initstate(unsigned int seed, char *state, size_t n); char *setstate(char *state);DESCRIPTION

The random() function uses a non-linear additive feedback random number generator employing a default table of size 31 long integers to return successive pseudo-random numbers in the range from 0 to RAND_MAX. The period of this random number generator is very large, approx- imately 16*((2**31)-1). The srandom() function sets its argument as the seed for a new sequence of pseudo-random integers to be returned by random(). These sequences are repeatable by calling srandom() with the same seed value. If no seed value is provided, the random() function is automati- cally seeded with a value of 1. The initstate() function allows a state array state to be initialized for use by random(). The size of the state array n is used by init- state() to decide how sophisticated a random number generator it should usethe larger the state array, the better the random numbers will be. seed is the seed for the initialization, which specifies a starting point for the random number sequence, and provides for restarting at the same point. The setstate() function changes the state array used by the random() function. The state array state is used for random number generation until the next call to initstate() or setstate(). state must first have been initialized using initstate() or be the result of a previous call of setstate().--RETURN VALUE

The random() function returns a value between 0 and RAND_MAX. The srandom() function returns no value. The initstate() and setstate() functions return a pointer to the previous state array, or NULL on error.ERRORS

EINVAL A state array of less than 8 bytes was specified to initstate().NOTES

Current "optimal" values for the size of the state array n are 8, 32, 64, 128, and 256 bytes; other amounts will be rounded down to the nearest known amount. Using less than 8 bytes will cause an error.CONFORMING TO

BSD 4.3SEE ALSO

rand(3), srand(3)GNU

2000-08-20 RANDOM(3)