- Yioop Repo - Seekquarry

<?php
/**
 * SeekQuarry/Yioop --
 * Open Source Pure PHP Search Engine, Crawler, and Indexer
 *
 * Copyright (C) 2009 - 2026  Chris Pollett chris@pollett.org
 *
 * LICENSE:
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * @author Chris Pollett chris@pollett.org
 * @license https://www.gnu.org/licenses/ GPL3
 * @link https://www.seekquarry.com/
 * @copyright 2009 - 2026
 * @filesource
 */
namespace seekquarry\yioop\tests;

use seekquarry\yioop\library\data_structures\LinearAlgebra;
use seekquarry\yioop\library\summarizers\CentroidWeightedSummarizer;
use seekquarry\yioop\library\UnitTest;

/**
 * CentroidWeightedSummarizerTest checks how CentroidWeightedSummarizer
 * picks the sentences of a page's summary.
 *
 * @author Chris Pollett
 */
class CentroidWeightedSummarizerTest extends UnitTest
{
    /**
     * setUp does nothing, since each case makes its own sentences.
     */
    public function setUp()
    {
    }
    /**
     * tearDown does nothing, since a case leaves nothing behind.
     */
    public function tearDown()
    {
    }
    /**
     * picksMatchScoringEverySentenceAgainTestCase checks that
     * scoreSentencesVersusAverage, which scores each sentence once and
     * then lowers only the scores a pick changes, picks the same sentences
     * with the same scores as scoring every sentence again after each
     * pick. The sentences share words, and one is given twice, so picks
     * change other sentences' scores.
     */
    public function picksMatchScoringEverySentenceAgainTestCase()
    {
        $texts = ["red apple sweet fruit", "green apple sour fruit",
            "red car fast", "red apple sweet fruit", "blue sky clear",
            "fruit market sells apple pear", "fast red train"];
        $vectors = [];
        foreach ($texts as $text) {
            $vectors[] = LinearAlgebra::normalize(array_count_values(
                explode(" ", $text)));
        }
        $average = CentroidWeightedSummarizer::getAverageSentence($vectors);
        $picked = CentroidWeightedSummarizer::scoreSentencesVersusAverage(
            $vectors, $average);
        $expected = self::scoreEverySentenceAgain($vectors, $average);
        $this->assertEqual(array_keys($picked), array_keys($expected),
            "the same sentences are picked in the same order");
        $close = true;
        foreach ($expected as $sentence => $score) {
            $close = $close && abs($picked[$sentence] - $score) < 1e-9;
        }
        $this->assertTrue($close, "each pick has the same score");
    }
    /**
     * scoreEverySentenceAgain picks sentences as scoreSentencesVersusAverage
     * did before it kept its scores: each pick works out the inner product
     * of the average with every sentence left, takes the largest, and
     * takes that sentence's direction out of the average.
     *
     * @param array $vectors normalized term vectors of the sentences
     * @param array $average the normalized average sentence
     * @return array sentence index => score, in the order picked
     */
    public static function scoreEverySentenceAgain($vectors, $average)
    {
        $picked = [];
        $best = 1;
        while ($best > 0) {
            $best = -1;
            $best_index = -1;
            foreach ($vectors as $sentence => $vector) {
                $score = LinearAlgebra::dot($average, $vector);
                if ($best < $score) {
                    $best = $score;
                    $best_index = $sentence;
                }
            }
            if ($best > -1) {
                $picked[$best_index] = $best;
                foreach ($vectors[$best_index] as $term => $weight) {
                    $average[$term] -= $average[$term] * $weight;
                }
                unset($vectors[$best_index]);
            }
        }
        return $picked;
    }
}