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| Newer page: | version 2 | Last edited on Friday, March 26, 2004 8:14:39 am | by JohnMcPherson | Revert |
| Older page: | version 1 | Last edited on Tuesday, June 4, 2002 12:24:17 am | by perry | Revert |
@@ -1,117 +1 @@
-DRAND48
-!!!DRAND48
-NAME
-SYNOPSIS
-DESCRIPTION
-CONFORMING TO
-NOTES
-SEE ALSO
-----
-!!NAME
-
-
-drand48, erand48, lrand48, nrand48, mrand48, jrand48, srand48, seed48, lcong48 - generate uniformly distributed pseudo-random numbers
-!!SYNOPSIS
-
-
-__#include
-__ ''xsubi''__[[3]);
-long int lrand48(void);
-long int nrand48(unsigned short int__ ''xsubi''__[[3]);
-long int mrand48(void);
-long int jrand48(unsigned short int__ ''xsubi''__[[3]);
-void srand48(long int__ ''seedval''__);
-unsigned short int *__''seed48(unsigned''__short__''int'' __seed16v [[3]);
-void lcong48(unsigned short int__ ''param''__[[7]);
-__
-!!DESCRIPTION
-
-
-These functions generate pseudo-random numbers using
the
-linear congruential algorithm and 48-bit integer
-arithmetic.
-
-
-The __
drand48()__ and __erand48()__ functions return
-non-negative double-precision floating-point values
-uniformly distributed between [[., 1.).
-
-
-The __lrand48()__ and __nrand48()__ functions return
-non-negative long integers uniformly distributed between
-and 2^31.
-
-
-The __mrand48()__ and __jrand48()__ functions return
-signed long integers uniformly distributed between -2^31 and
-2^31.
-
-
-The __srand48()__, __seed48()__ and __lcong48()__
-functions are initialization functions, one of which should
-be called before using __drand48()__, __lrand48()__ or
-__mrand49()__. The functions __erand48()__,
-__nrand48()__ and __jrand48()__ do not require an
-initialization function to be called first.
-
-
-All the functions work by generating a sequence of 48-bit
-integers, ''Xi'', according to the linear congruential
-formula:
-
-
-__ Xn+1 = (aXn + c) mod m, where n
-__The parameter ''m'' = 2^48, hence 48-bit integer arithmetic is performed. Unless __lcong48()__ is called, ''a'' and ''c'' are given by:
-
-
-__ a = 0x5DEECE66D
-c = 0xB
-__The value returned by any of the functions __drand48()__, __erand48()__, __lrand48()__, __nrand48()__, __mrand48()__ or __jrand48()__ is computed by first generating the next 48-bit ''Xi'' in the sequence. Then the appropriate number of bits, according to the type of data item to be returned, is copied from the high-order bits of ''Xi'' and transformed into the returned value.
-
-
-The functions __drand48()__, __lrand48()__ and
-__mrand48()__ store the last 48-bit ''Xi'' generated
-in an internal buffer. The functions __erand48()__,
-__nrand48()__ and __jrand48()__ require the calling
-program to provide storage for the successive ''Xi''
-values in the array argument ''xsubi''. The functions are
-initialized by placing the initial value of ''Xi'' into
-the array before calling the function for the first
-time.
-
-
-The initializer function __srand48()__ sets the high
-order 32-bits of ''Xi'' to the argument ''seedval''.
-The low order 16-bits are set to the arbitrary value
-0x330E.
-
-
-The initializer function __seed48()__ sets the value of
-''Xi'' to the 48-bit value specified in the array
-argument ''seed16v''. The previous value of ''Xi'' is
-copied into an internal buffer and a pointer to this buffer
-is returned by __seed48()__.
-
-
-The initialization function __lcong48()__ allows the user
-to specify initial values for ''Xi'', ''a'' and
-''c''. Array argument elements ''param[[-2]'' specify
-''Xi'', ''param[[
3-5]'' specify ''a'', and
-''param[[6]'' specifies ''c''. After __lcong48(
)__
-has been called, a subsequent call to either
-__srand48()__ or __seed48()__ will restore the
-standard values of ''a'' and ''c''
.
-!!CONFORMING TO
-
-
-SVID 3
-!!NOTES
-
-
-These functions are declared obsolete by SVID 3, which
-states that rand(3) should be used instead.
-!!SEE ALSO
-
-
-rand(3), random(3)
-----
+See
the drand48(3) man page
.
