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+.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
+.TH "DRAND48" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
+.\" drand48 
+.SH NAME
+drand48, erand48, jrand48, lcong48, lrand48, mrand48, nrand48, seed48,
+srand48 \- generate uniformly distributed
+pseudo\-random numbers
+.SH SYNOPSIS
+.LP
+\fB#include <stdlib.h>
+.br
+.sp
+double drand48(void);
+.br
+double erand48(unsigned short\fP \fIxsubi\fP\fB[3]);
+.br
+long jrand48(unsigned short\fP \fIxsubi\fP\fB[3]);
+.br
+void lcong48(unsigned short\fP \fIparam\fP\fB[7]);
+.br
+long lrand48(void);
+.br
+long mrand48(void);
+.br
+long nrand48(unsigned short\fP \fIxsubi\fP\fB[3]);
+.br
+unsigned short *seed48(unsigned short\fP \fIseed16v\fP\fB[3]);
+.br
+void srand48(long\fP \fIseedval\fP\fB); \fP
+\fB
+.br
+\fP
+.SH DESCRIPTION
+.LP
+This family of functions shall generate pseudo-random numbers using
+a linear congruential algorithm and 48-bit integer
+arithmetic.
+.LP
+The \fIdrand48\fP() and \fIerand48\fP() functions shall return non-negative,
+double-precision, floating-point values,
+uniformly distributed over the interval [0.0,1.0).
+.LP
+The \fIlrand48\fP() and \fInrand48\fP() functions shall return non-negative,
+long integers, uniformly distributed over the
+interval [0,2**31).
+.LP
+The \fImrand48\fP() and \fIjrand48\fP() functions shall return signed
+long integers uniformly distributed over the interval
+[-2**31,2**31).
+.LP
+The \fIsrand48\fP(), \fIseed48\fP(), and \fIlcong48\fP() functions
+are initialization entry points, one of which should be
+invoked before either \fIdrand48\fP(), \fIlrand48\fP(), or \fImrand48\fP()
+is called. (Although it is not recommended practice,
+constant default initializer values shall be supplied automatically
+if \fIdrand48\fP(), \fIlrand48\fP(), or \fImrand48\fP() is
+called without a prior call to an initialization entry point.) The
+\fIerand48\fP(), \fInrand48\fP(), and \fIjrand48\fP()
+functions do not require an initialization entry point to be called
+first.
+.LP
+All the routines work by generating a sequence of 48-bit integer values,
+X_i , according to the linear congruential
+formula:
+X_n+1 = (aX_n + c)_mod m\ \ \ n>= 0
+.LP
+The parameter \fIm\fP = 2**48; hence 48-bit integer arithmetic is
+performed. Unless \fIlcong48\fP() is invoked, the multiplier
+value \fIa\fP and the addend value \fIc\fP are given by:
+\fIa\fP = 5DEECE66D_16 = 273673163155_8
+.LP
+\fIc\fP = B_16 = 13_8
+.LP
+The value returned by any of the \fIdrand48\fP(), \fIerand48\fP(),
+\fIjrand48\fP(), \fIlrand48\fP(), \fImrand48\fP(), or
+\fInrand48\fP() functions is computed by first generating the next
+48-bit X_i in the sequence. Then the appropriate number
+of bits, according to the type of data item to be returned, are copied
+from the high-order (leftmost) bits of X_i and
+transformed into the returned value.
+.LP
+The \fIdrand48\fP(), \fIlrand48\fP(), and \fImrand48\fP() functions
+store the last 48-bit X_i generated in an internal
+buffer; that is why the application shall ensure that these are initialized
+prior to being invoked. The \fIerand48\fP(),
+\fInrand48\fP(), and \fIjrand48\fP() functions require the calling
+program to provide storage for the successive X_i values
+in the array specified as an argument when the functions are invoked.
+That is why these routines do not have to be initialized; the
+calling program merely has to place the desired initial value of X_i
+into the array and pass it as an argument. By using
+different arguments, \fIerand48\fP(), \fInrand48\fP(), and \fIjrand48\fP()
+allow separate modules of a large program to generate
+several \fIindependent\fP streams of pseudo-random numbers; that is,
+the sequence of numbers in each stream shall \fInot\fP
+depend upon how many times the routines are called to generate numbers
+for the other streams.
+.LP
+The initializer function \fIsrand48\fP() sets the high-order 32 bits
+of X_i to the low-order 32 bits contained in its
+argument. The low-order 16 bits of X_i are set to the arbitrary value
+330E_16.
+.LP
+The initializer function \fIseed48\fP() sets the value of X_i to the
+48-bit value specified in the argument array. The
+low-order 16 bits of X_i are set to the low-order 16 bits of \fIseed16v\fP[\fI0\fP].
+The mid-order 16 bits of X_i are
+set to the low-order 16 bits of \fIseed16v\fP[\fI1\fP]. The high-order
+16 bits of X_i are set to the low-order 16 bits of
+\fIseed16v\fP[\fI2\fP]. In addition, the previous value of X_i is
+copied into a 48-bit internal buffer, used only by
+\fIseed48\fP(), and a pointer to this buffer is the value returned
+by \fIseed48\fP(). This returned pointer, which can just be
+ignored if not needed, is useful if a program is to be restarted from
+a given point at some future time-use the pointer to get at
+and store the last X_i value, and then use this value to reinitialize
+via \fIseed48\fP() when the program is restarted.
+.LP
+The initializer function \fIlcong48\fP() allows the user to specify
+the initial X_i , the multiplier value \fIa\fP, and the
+addend value \fIc\fP. 
+Argument array elements \fIparam\fP[\fI0-2\fP] specify X_i , \fIparam\fP[\fI3-5\fP]
+specify the
+multiplier \fIa\fP, and \fIparam\fP[\fI6\fP] specifies the 16-bit
+addend \fIc\fP. After \fIlcong48\fP() is called, a subsequent call
+to
+either \fIsrand48\fP() or \fIseed48\fP() shall restore the standard
+multiplier and addend values, \fIa\fP and \fIc,\fP
+specified above.
+.LP
+The \fIdrand48\fP(), \fIlrand48\fP(), and \fImrand48\fP() functions
+need not be reentrant. A function that is not required to
+be reentrant is not required to be thread-safe.
+.SH RETURN VALUE
+.LP
+As described in the DESCRIPTION above.
+.SH ERRORS
+.LP
+No errors are defined.
+.LP
+\fIThe following sections are informative.\fP
+.SH EXAMPLES
+.LP
+None.
+.SH APPLICATION USAGE
+.LP
+None.
+.SH RATIONALE
+.LP
+None.
+.SH FUTURE DIRECTIONS
+.LP
+None.
+.SH SEE ALSO
+.LP
+\fIrand\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
+\fI<stdlib.h>\fP
+.SH COPYRIGHT
+Portions of this text are reprinted and reproduced in electronic form
+from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
+-- Portable Operating System Interface (POSIX), The Open Group Base
+Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
+Electrical and Electronics Engineers, Inc and The Open Group. In the
+event of any discrepancy between this version and the original IEEE and
+The Open Group Standard, the original IEEE and The Open Group Standard
+is the referee document. The original Standard can be obtained online at
+http://www.opengroup.org/unix/online.html .