ExpireLRU(3)

NAME
Memoize - Expiry plug-in for Memoize that adds LRU cache expiration

SYNOPSIS
    use Memoize;

    memoize('slow_function',
            TIE => [Memoize::ExpireLRU,
                    CACHESIZE => n,
                   ]);

Note that one need not "use" this module. It will be found by the Memoize module.

The argument to CACHESIZE must be an integer. Normally, this is all that is needed. Additional options are available:

        TUNECACHESIZE => m,
        INSTANCE => 'descriptive_name',
        TIE => '[DB_File, $filename, O_RDWR | O_CREATE, 0666]'

DESCRIPTION
For the theory of Memoization, please see the Memoize module documentation. This module implements an expiry policy for Memoize that follows LRU semantics, that is, the last n results, where n is specified as the argument to the "CACHESIZE" parameter, will be cached.

PERFORMANCE TUNING
It is often quite difficult to determine what size cache will give optimal results for a given function. To aid in determining this, ExpireLRU includes cache tuning support. Enabling this causes a definite performance hit, but it is often useful before code is released to production.

To enable cache tuning support, simply specify the optional "TUNECACHESIZE" parameter with a size greater than that of the "CACHESIZE" parameter.

When the program exits, a set of statistics will be printed to stderr. If multiple routines have been memoized, separate sets of statistics are printed for each routine. The default names are somewhat cryptic: this is the purpose of the "INSTANCE" parameter. The value of this parameter will be used as the identifier within the statistics report.

DIAGNOSTIC METHODS
Two additional routines are available but not exported. Memoize::ExpireLRU::ShowStats returns a string identical to the statistics report printed to STDERR at the end of the program if test caches have been enabled; Memoize::ExpireLRU::DumpCache takes the instance name of a memoized function as a parameter, and returns a string describing the current state of that instance.

AUTHOR
Brent B. Powers (B2Pi), Powers@B2Pi.com

Copyright(c) 1999 Brent B. Powers. All rights reserved. This program is free software, you may redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO
Memoize