random
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 | This is the JargonFile (V4.00) entry for random - Next: random numbers, Prev: rainbow series |
| :random: /adj./ 1. Unpredictable (closest to mathematical definition); weird. "The systems been behaving pretty randomly." 2. Assorted; undistinguished. "Who was at the conference?" "Just a bunch of random business types." 3. (pejorative) Frivolous; unproductive; undirected. "Hes just a random loser." 4. Incoherent or inelegant; poorly chosen; not well organized. "The program has a random set of misfeatures." "Thats a random name for that function." "Well, all the names were chosen pretty randomly." 5. In no particular order, though deterministic. "The I/O channels are in a pool, and when a file is opened one is chosen randomly." 6. Arbitrary. "It generates a random name for the scratch file." 7. Gratuitously wrong, i.e., poorly done and for no good apparent reason. For example, a program that handles file name defaulting in a particularly useless way, or an assembler routine that could easily have been coded using only three registers, but redundantly uses seven for values with non-overlapping lifetimes, so that no one else can invoke it without first saving four extra registers. What randomness! 8. /n./ A random hacker; used particularly of high-school students who soak up computer time and generally get in the way. 9. n. Anyone who is not a hacker (or, sometimes, anyone not known to the hacker speaking); the noun form of sense 2. "I went to the talk, but the audience was full of randoms asking bogus questions". 10. /n./ (occasional MIT usage) One who lives at Random Hall. See also J. Random, some random X. | |
| * (text is auto-included via JargonExtension by mutante using jargon with VERSION 4.0.0, 24 JUL 1996 - JargonFile by Eric S. Raymond is in the public domain) | |
| Table of contents |
NAME
random, srandom, initstate, setstate - random number generatorSYNOPSIS
#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 "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
4.3BSD, POSIX.1-2001.SEE ALSO
rand(3), srand(3)
Index
Updated Time:: 05:37:23 GMT, July 09, 2008
