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!!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, approximately
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
automatically 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
__initstate()__ to decide how sophisticated a random
number generator it should use -- the 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
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 4.3
!!SEE ALSO


rand(3), srand(3), [random(3)], [random(4)],  [srandom(3)] and [urandom(4)]
----

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Last edited on Thursday, September 11, 2003 1:22:56 pm by StuartYeates

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