diff options
Diffstat (limited to 'lib/libc/stdlib/random.3')
| -rw-r--r-- | lib/libc/stdlib/random.3 | 39 |
1 files changed, 22 insertions, 17 deletions
diff --git a/lib/libc/stdlib/random.3 b/lib/libc/stdlib/random.3 index 260c2398164..d3a3198ebfb 100644 --- a/lib/libc/stdlib/random.3 +++ b/lib/libc/stdlib/random.3 @@ -29,7 +29,7 @@ .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" -.\" $OpenBSD: random.3,v 1.11 2000/04/03 23:23:48 millert Exp $ +.\" $OpenBSD: random.3,v 1.12 2000/04/20 13:50:02 aaron Exp $ .\" .Dd April 19, 1991 .Dt RANDOM 3 @@ -56,23 +56,27 @@ .Sh DESCRIPTION The .Fn 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 +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 (2**31)\-1. The period of this random number generator is very large, approximately 16*((2**31)\-1. .Pp The -.Fn random Ns / Fn srandom -have (almost) the same calling sequence and initialization properties as +.Fn random +and +.Fn srandom +functions have (almost) the same calling sequence and initialization +properties as .Xr rand 3 Ns / Xr srand 3 . The difference is that .Xr rand produces a much less random sequence \(em in fact, the low dozen bits -generated by rand go through a cyclic pattern. All the bits generated by +generated by rand go through a cyclic pattern. +All the bits generated by .Fn random -are usable. For example, +are usable. +For example, .Sq Li random()&01 will produce a random binary value. @@ -81,9 +85,10 @@ Unlike .Xr srand , .Fn srandom 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 +state information used is much more than a single word. +(Two other routines are provided to deal with restarting/changing random +number generators). +Like .Xr rand 3 , however, .Fn random @@ -110,28 +115,28 @@ a fixed seed. The .Fn initstate 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 +for future use. +The size of the state array (in bytes) is used by .Fn initstate to decide how sophisticated a random number generator it should use \(em the more state, the better the random numbers will be. (Current "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 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. The .Fn initstate -function -returns a pointer to the previous state information array. +function returns a pointer to the previous state information array. .Pp Once a state has been initialized, the .Fn setstate routine provides for rapid switching between states. The .Fn setstate -function -returns a pointer to the previous state array; its +function returns a pointer to the previous state array; its argument state array is used for further random number generation until the next call to .Fn initstate |