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Perl Cookbook
book

Perl Cookbook

by Tom Christiansen, Nathan Torkington
August 1998
Intermediate to advanced content levelIntermediate to advanced
800 pages
39h 20m
English
O'Reilly Media, Inc.
Content preview from Perl Cookbook

Making Numbers Even More Random

Problem

You want to generate numbers that are more random than Perl’s random numbers. Limitations of your C library’s random number generator seeds will sometimes cause problems. The sequence of pseudo-random numbers may repeat too soon for some applications.

Solution

Use a different random number generator, such as those provided by the Math::Random and Math::TrulyRandom modules from CPAN:

use Math::TrulyRandom;
$random = truly_random_value();

use Math::Random;
$random = random_uniform();

Discussion

Perl uses the standard C library routine rand(3) to generate pseudo-random numbers. (This can be changed at build time, however.) Some implementations of the rand function return only 16-bit random numbers or have algorithmic weaknesses and may not be sufficiently random.

The Math::TrulyRandom module uses the inadequacies of your system’s timers to generate the random numbers. This takes a while, so it isn’t useful for generating a lot of random numbers.

The Math::Random module uses the randlib library to generate random numbers. It also includes a wide range of related functions.

See Also

The srand and rand functions in perlfunc(1) and Chapter 3 of Programming Perl; Section 2.7; Section 2.8; the documentation for the CPAN modules Math::Random and Math::TrulyRandom

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Publisher Resources

ISBN: 1565922433Supplemental ContentCatalog PageErrata