.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\" 386BSD man pages
.\" Modified Sat Jul 24 19:46:03 1993 by Rik Faith (faith@cs.unc.edu)
-.TH DRAND48 3 2007-07-26 "" "Linux Programmer's Manual"
+.TH DRAND48 3 2013-06-21 "" "Linux Programmer's Manual"
.SH NAME
drand48, erand48, lrand48, nrand48, mrand48, jrand48, srand48, seed48,
lcong48 \- generate uniformly distributed pseudo-random numbers
an initialization function to be called first.
.PP
All the functions work by generating a sequence of 48-bit integers,
-\fIXi\fP, according to the linear congruential formula:
+.IR Xi ,
+according to the linear congruential formula:
.sp
.nf
.RS
.RE
.fi
.sp
-The parameter \fIm\fP = 2^48, hence 48-bit integer arithmetic is performed.
+The parameter
+.I m
+= 2^48, hence 48-bit integer arithmetic is performed.
Unless
.BR lcong48 ()
-is called, \fIa\fP and \fIc\fP are given by:
+is called,
+.IR a
+and
+.I c
+are given by:
.sp
.nf
.RS
or
.BR jrand48 ()
is
-computed by first generating the next 48-bit \fIXi\fP in the sequence.
+computed by first generating the next 48-bit
+.I 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 \fIXi\fP and transformed
+be returned, is copied from the high-order bits of
+.I Xi
+and transformed
into the returned value.
.PP
The functions
and
.BR mrand48 ()
store
-the last 48-bit \fIXi\fP generated in an internal buffer.
+the last 48-bit
+.I Xi
+generated in an internal buffer.
The functions
.BR erand48 (),
.BR nrand48 ()
and
.BR jrand48 ()
require the calling
-program to provide storage for the successive \fIXi\fP values in the array
-argument \fIxsubi\fP.
+program to provide storage for the successive
+.I Xi
+values in the array
+argument
+.IR xsubi .
The functions are initialized by placing the initial
-value of \fIXi\fP into the array before calling the function for the first
+value of
+.I Xi
+into the array before calling the function for the first
time.
.PP
The initializer function
.BR srand48 ()
sets the high order 32-bits of
-\fIXi\fP to the argument \fIseedval\fP.
+.I Xi
+to the argument
+.IR seedval .
The low order 16-bits are set
to the arbitrary value 0x330E.
.PP
The initializer function
.BR seed48 ()
-sets the value of \fIXi\fP to
-the 48-bit value specified in the array argument \fIseed16v\fP.
+sets the value of
+.I Xi
+to
+the 48-bit value specified in the array argument
+.IR seed16v .
The
-previous value of \fIXi\fP is copied into an internal buffer and a
+previous value of
+.I Xi
+is copied into an internal buffer and a
pointer to this buffer is returned by
.BR seed48 ().
.PP
The initialization function
.BR lcong48 ()
allows the user to specify
-initial values for \fIXi\fP, \fIa\fP and \fIc\fP.
+initial values for
+.IR Xi ,
+.I a
+and
+.IR c .
Array argument
-elements \fIparam[0-2]\fP specify \fIXi\fP, \fIparam[3-5]\fP specify
-\fIa\fP, and \fIparam[6]\fP specifies \fIc\fP.
+elements
+.I param[0-2]
+specify
+.IR Xi ,
+.I param[3-5]
+specify
+.IR a ,
+and
+.I param[6]
+specifies
+.IR c .
After
.BR lcong48 ()
has been called, a subsequent call to either
.BR srand48 ()
or
.BR seed48 ()
-will restore the standard values of \fIa\fP and \fIc\fP.
+will restore the standard values of
+.I a
+and
+.IR c .
+.SH ATTRIBUTES
+.SS Multithreading (see pthreads(7))
+The
+.BR drand48 (),
+.BR erand48 (),
+.BR lrand48 (),
+.BR nrand48 (),
+.BR mrand48 (),
+.BR jrand48 (),
+.BR srand48 (),
+.BR seed48 (),
+and
+.BR lcong48 ()
+functions record global state information for the random number generator,
+so they are not thread-safe.
.SH CONFORMING TO
SVr4, POSIX.1-2001.
.SH NOTES
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