Memoize

This make a Perl 6 routine faster by caching its results. This means it trades more memory space used to get less execution time on cache hits. This means it is faster on routines that return a result such the following:

• An expensive calculation (CPU)
• A slow database query (I/O)

This is a totally-experimental-at-the-moment module to create a subroutine trait similar to the currently experimental is cached.

Plan

• Add None to strategy to disable cache eviction and cache size limitation
• Determine tunable cache size statistics
• Add a pluggable architecture to cache expiry.

perlpilot: it would be interesting if you could pass the thing that handles the caching as a parameter, but perhaps only as an academic exercise.

Example

use v6;
use Memoize;

sub get-slowed-result(Int $n where $_ >= 0) is memoized {
  sleep $n / 10;
  return 1 if $n <= 1;
  return get-slowed-result($n - 1) * $n;
}

say sprintf("get-slowed-result(%d) is %d", $_, get-slowed-result($_)) for 0..10;

Memoize vs is-cached

• is-cached is currently marked as experimental as per a #perl6 discussion.

Here is an example for is cached for the sake of completeness:

#!/usr/bin/env perl6

use v6;
use experimental :cached;

sub get-slowed-result(Int $n where $_ >= 0) is cached {
  sleep $n / 10;
  return 1 if $n <= 1;
  return get-slowed-result($n - 1) * $n;
}

say sprintf("get-slowed-result(%d) is %d", $_, get-slowed-result($_)) for 0..10;

See Also

• Add memoize to Perl 6 Most Wanted
• Memoize (CPAN)
• Memoize::ExpireLRU (CPAN)
• Perl 6 RFC 228 - Add memoize into the standard library
• Design specification for is cached subroutine trait
• Perl 6 documentation for is cached subroutine trait
• Memoization on Wikipedia
• Pure and impure functions on Wikipedia

Author

Ahmad M. Zawawi, azawawi on #perl6, https://github.com/azawawi/

License

MIT License