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<html>
<head>
<title>
RAND48 - 48-bit Random Number Generators
</title>
</head>
<body bgcolor="#EEEEEE" link="#CC0000" alink="#FF3300" vlink="#000055">
<h1 align = "center">
RAND48 <br> 48-bit Random Number Generators
</h1>
<hr>
<p>
<b>RAND48</b>
is a C++ library which
demonstrates the use of the rand48 function in the C <b>stdlib</b> library.
The rand48 function uses 48-bit arithmetic to generate uniformly distributed pseudorandom
values. The results can be returned as double precision values
in [0.0,1.0], or as long integers in [-2^31,2^31], or as nonnegative long
integers in [0,2^31].
</p>
<p>
The underlying calculations are done in 48-bit integer arithmetic.
The user has the option of allowing the system to select the initial seed,
or of supplying 32 bits of the seed as a long int, or supplying all 48 bits
of the seed as 3 16 bit values. The user can also supply the seed as
an explicit argument on each call, or make a single initialization call
with the desired seed.
</p>
<p>
Routines to set the seed:
<ul>
<li>
<b>void srand48(long int seedval)</b>, <br>
the user passes in a long int. The 32 bits of this
value are used, along with 16 bits supplied internally. This is the
most convenient routine to call.
</li>
<li>
<b>unsigned short int *seed48(unsigned short int seedvec[3])</b>,<br>
the user passes in 3 16 bit values which completely
determine the seed. This gives the user full control over the seed.
</li>
<li>
<b>void lcong48(unsigned short int param[7])</b>, <br>
allows the user to specify the seed as in <b>seed48</b>,
but also the 48 bit multiplier and 16 bit addend used in the linear
congruential generator.
</li>
</ul>
</p>
<p>
There are 3 routines available which return a random value, assuming that
the seed has been set in advance by a call to <b>srand48</b>, <b>seed48</b>, or
<b>lcong48</b>, or that the user is satisfied with a
default seed value. These routines have no input argument.
<ul>
<li>
<b>double drand48(void)</b><br>
returns a double precision floating point value in [0.0,1.0];
</li>
<li>
<b>long int lrand48(void)</b>,<br>
returns a nonnegative long integer in [0,2^31];
</li>
<li>
<b>long int mrand48(void)</b>, <br>
returns a long integer in [-2^31,2^31];
</li>
</ul>
</p>
<p>
There are 3 routines available which return a random value, whose computation
is determined by the value of the seed vector in the input argument.
These routines do not require the user to call a seed initialization routine first.
<ul>
<li>
<b>double erand48(unsigned short int seedvec[3])</b><br>
returns a double precision floating point value in [0.0,1.0];
</li>
<li>
<b>long int nrand48(unsigned short int seedvec[3])</b>,<br>
returns a nonnegative long integer in [0,2^31];
</li>
<li>
<b>long int jrand48(unsigned short int seedvec[3])</b>, <br>
returns a long integer in [-2^31,2^31];
</li>
</ul>
</p>
<h3 align = "center">
Licensing:
</h3>
<p>
The computer code and data files described and made available on this web page
are distributed under
<a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
</p>
<h3 align = "center">
Languages:
</h3>
<p>
<b>RAND48</b> is available in
<a href = "../../c_src/rand48/rand48.html">a C version</a> and
<a href = "../../cpp_src/rand48/rand48.html">a C++ version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../cpp_src/asa183/asa183.html">
ASA183</a>,
a C++ library which
implements the Wichman-Hill pseudorandom number generator.
</p>
<p>
<a href = "../../cpp_src/cpp_random/cpp_random.html">
CPP_RANDOM</a>,
C++ programs which
illustrate the use of the C++ random number generator routines.
</p>
<p>
<a href = "../../cpp_src/faure/faure.html">
FAURE</a>,
a C++ library which
computes elements of a Faure quasirandom sequence.
</p>
<p>
<a href = "../../cpp_src/halton/halton.html">
HALTON</a>,
a C++ library which
computes elements of a Halton quasirandom sequence.
</p>
<p>
<a href = "../../cpp_src/hammersley/hammersley.html">
HAMMERSLEY</a>,
a C++ library which
computes elements of a Hammersley quasirandom sequence.
</p>
<p>
<a href = "../../cpp_src/niederreiter2/niederreiter2.html">
NIEDERREITER2</a>,
a C++ library which
computes elements of a Niederreiter sequence using base 2.
</p>
<p>
<a href = "../../cpp_src/normal/normal.html">
NORMAL</a>,
a C++ library which
computes elements of a sequence of pseudorandom normally distributed values.
</p>
<p>
<a href = "../../cpp_src/ranlib/ranlib.html">
RANLIB</a>,
a C++ library which
produces random samples from Probability Density Functions (PDF's),
including Beta, Chi-square Exponential, F, Gamma, Multivariate normal,
Noncentral chi-square, Noncentral F, Univariate normal, random permutations,
Real uniform, Binomial, Negative Binomial, Multinomial, Poisson
and Integer uniform,
by Barry Brown and James Lovato.
</p>
<p>
<a href = "../../cpp_src/sobol/sobol.html">
SOBOL</a>,
a C++ library which
computes elements of a Sobol quasirandom sequence.
</p>
<p>
<a href = "../../cpp_src/uniform/uniform.html">
UNIFORM</a>,
a C++ library which
computes elements of a sequence of pseudorandom uniformly distributed values.
</p>
<p>
<a href = "../../cpp_src/van_der_corput/van_der_corput.html">
VAN_DER_CORPUT</a>,
a C++ library which
computes elements of a 1D van der Corput sequence.
</p>
<h3 align = "center">
Reference:
</h3>
<p>
<ol>
<li>
Donald Knuth,<br>
The Art of Computer Programming,<br>
Volume 2, Seminumerical Algorithms,<br>
Third Edition,<br>
Addison Wesley, 1997,<br>
ISBN: 0201896842,<br>
LC: QA76.6.K64.
</li>
</ol>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
<ul>
<li>
<a href = "rand48_prb.cpp">rand48_prb.cpp</a>,
a sample calling program.
</li>
<li>
<a href = "rand48_prb.sh">rand48_prb.sh</a>,
commands to compile, link and run the sample calling program.
</li>
<li>
<a href = "rand48_prb_output.txt">rand48_prb_output.txt</a>,
the output file.
</li>
</ul>
</p>
<p>
You can go up one level to <a href = "../cpp_src.html">
the C++ source codes</a>.
</p>
<hr>
<i>
Last revised on 18 August 2008.
</i>
<!-- John Burkardt -->
</body>
</html>