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t/33-parallel-fit.t  view on Meta::CPAN

#!perl
# 33-parallel-fit.t
#
# Verifies the parallel_fit option:
#   1. Produces a fitted model with the requested number of trees.
#   2. score_samples on a held-out point looks like a normal score
#      (between 0 and 1, and clearly separates an obvious outlier).
#   3. Re-running the parallel fit with the same seed and worker count
#      gives bit-identical scores (cross-run reproducibility, which is
#      the parallel_fit contract -- serial-vs-parallel differs but
#      parallel-vs-parallel does not).
#   4. parallel_fit on a no-fork platform falls back silently to serial.

use strict;
use warnings;
use Test::More;
use List::Util qw(min max);
use Config;

use Algorithm::Classifier::IsolationForest;

my $CLASS = 'Algorithm::Classifier::IsolationForest';

# Build a deterministic dataset.
sub gaussian {
	my ( $mu, $sigma ) = @_;
	my $u1 = rand() || 1e-12;
	my $u2 = rand();
	return $mu + $sigma * sqrt( -2 * log($u1) ) * cos( 2 * 3.14159265358979 * $u2 );
}

srand(20260629);
my @train;
push @train, [ gaussian( 0, 1 ), gaussian( 0, 1 ), gaussian( 0, 1 ) ] for 1 .. 300;
push @train, [  8, -8,  7 ];
push @train, [ -7,  8, -8 ];

my @query = (
	[ 0.1, -0.2, 0.0 ],    # inlier-like
	[ 9,    9,   9 ],      # obvious outlier
);

my $can_fork = ( $Config{d_fork} || '' ) eq 'define';

subtest 'parallel_fit produces a valid model' => sub {
	plan skip_all => 'no fork() on this platform' unless $can_fork;

	my $f = $CLASS->new(
		n_trees      => 50,
		sample_size  => 256,
		seed         => 42,
		parallel_fit => 4,
	);
	$f->fit( \@train );

	is( scalar @{ $f->{trees} }, 50, 'tree count matches n_trees' );

	my $s = $f->score_samples( \@query );
	is( scalar @$s, 2, 'two scores returned' );
	cmp_ok( $s->[0], '>=', 0,       'inlier score >= 0' );
	cmp_ok( $s->[0], '<=', 1,       'inlier score <= 1' );
	cmp_ok( $s->[1], '>',  $s->[0], 'outlier scores strictly higher than inlier (parallel-fit model is sane)' );
}; ## end 'parallel_fit produces a valid model' => sub

subtest 'parallel_fit is reproducible across runs at fixed worker count' => sub {
	plan skip_all => 'no fork() on this platform' unless $can_fork;