setstate(3) [ultrix man page]
random(3) Library Functions Manual random(3) Name random, srandom, initstate, setstate - better random number generator; routines for changing generators Syntax long random() void srandom(seed) int seed; char *initstate(seed, state, n) unsigned seed; char *state; int n; char *setstate(state) char *state; Description The subroutine 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 (2**31)-1. The period of this random number generator is very large, approximately 16*((2**31)-1). The subroutines have (almost) the same calling sequence and initialization properties as The difference is that rand(3) produces a much less random sequence - in fact, the low dozen bits generated by rand go through a cyclic pattern. All the bits generated by are usable. For example, "random()&01" will produce a random binary value. Unlike does not return the old seed; the reason for this is that the amount of state information used is much more than a single word. (Two other routines are provided to deal with restarting/changing random number generators.) Like however, will by default produce a sequence of numbers that can be duplicated by calling with 1 as the seed. The routine allows a state array, passed in as an argument, to be initialized for future use. The size of the state array (in bytes) is used by to decide how sophisticated a random number generator it should use - the more state, the better the random numbers will be. (Cur- rent "optimal" values for the amount of state information 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). The seed for the initialization (which specifies a starting point for the random number sequence, and provides for restarting at the same point) is also an argument. returns a pointer to the previous state information array. Once a state has been initialized, the routine provides for rapid switching between states. The subroutine returns a pointer to the previ- ous state array; its argument state array is used for further random number generation until the next call to or Once a state array has been initialized, it may be restarted at a different point either by calling (with the desired seed, the state array, and its size) or by calling both (with the state array) and (with the desired seed). The advantage of calling both and is that the size of the state array does not have to be remembered after it is initialized. With 256 bytes of state information, the period of the random number generator is greater than 269, which should be sufficient for most purposes. Diagnostics If is called with less than 8 bytes of state information, or if detects that the state information has been garbled, error messages are printed on the standard error output. See Also rand(3) random(3)
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random(3) Library Functions Manual random(3) Name random, srandom, initstate, setstate - better random number generator; routines for changing generators Syntax long random() void srandom(seed) int seed; char *initstate(seed, state, n) unsigned seed; char *state; int n; char *setstate(state) char *state; Description The subroutine 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 (2**31)-1. The period of this random number generator is very large, approximately 16*((2**31)-1). The subroutines have (almost) the same calling sequence and initialization properties as The difference is that rand(3) produces a much less random sequence - in fact, the low dozen bits generated by rand go through a cyclic pattern. All the bits generated by are usable. For example, "random()&01" will produce a random binary value. Unlike does not return the old seed; the reason for this is that the amount of state information used is much more than a single word. (Two other routines are provided to deal with restarting/changing random number generators.) Like however, will by default produce a sequence of numbers that can be duplicated by calling with 1 as the seed. The routine allows a state array, passed in as an argument, to be initialized for future use. The size of the state array (in bytes) is used by to decide how sophisticated a random number generator it should use - the more state, the better the random numbers will be. (Cur- rent "optimal" values for the amount of state information 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). The seed for the initialization (which specifies a starting point for the random number sequence, and provides for restarting at the same point) is also an argument. returns a pointer to the previous state information array. Once a state has been initialized, the routine provides for rapid switching between states. The subroutine returns a pointer to the previ- ous state array; its argument state array is used for further random number generation until the next call to or Once a state array has been initialized, it may be restarted at a different point either by calling (with the desired seed, the state array, and its size) or by calling both (with the state array) and (with the desired seed). The advantage of calling both and is that the size of the state array does not have to be remembered after it is initialized. With 256 bytes of state information, the period of the random number generator is greater than 269, which should be sufficient for most purposes. Diagnostics If is called with less than 8 bytes of state information, or if detects that the state information has been garbled, error messages are printed on the standard error output. See Also rand(3) random(3)