cc.kave.commons.pointsto.evaluation.UsagePruning.java Source code

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Here is the source code for cc.kave.commons.pointsto.evaluation.UsagePruning.java

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/**
 * Copyright 2016 Simon Reu
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */
package cc.kave.commons.pointsto.evaluation;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Random;

import org.apache.commons.math3.distribution.EnumeratedDistribution;
import org.apache.commons.math3.random.RandomGenerator;
import org.apache.commons.math3.util.Pair;

import com.google.inject.Inject;

import cc.kave.commons.pointsto.stores.ProjectIdentifier;
import cc.recommenders.usages.Usage;

public class UsagePruning {

    private final RandomGenerator rndGenerator;

    @Inject
    public UsagePruning(RandomGenerator rndGenerator) {
        this.rndGenerator = rndGenerator;
    }

    /**
     * @return The number of pruned usages
     */
    public int prune(final int maxUsages, Map<ProjectIdentifier, List<Usage>> usages) {
        final int initialNumUsages = usages.values().stream().mapToInt(Collection::size).sum();
        int numUsages = initialNumUsages;

        if (numUsages > maxUsages) {
            Random rnd = new Random(rndGenerator.nextLong());
            List<Pair<ProjectIdentifier, Double>> projectUsageCounts = new ArrayList<>(usages.size());
            for (Map.Entry<ProjectIdentifier, List<Usage>> entry : usages.entrySet()) {
                projectUsageCounts.add(Pair.create(entry.getKey(), (double) entry.getValue().size()));
                Collections.shuffle(entry.getValue(), rnd);
            }
            EnumeratedDistribution<ProjectIdentifier> distribution = new EnumeratedDistribution<>(rndGenerator,
                    projectUsageCounts);

            while (numUsages > maxUsages) {
                ProjectIdentifier project = distribution.sample();
                List<Usage> projectUsages = usages.get(project);
                if (!projectUsages.isEmpty()) {
                    projectUsages.remove(projectUsages.size() - 1);
                    --numUsages;
                }
            }
        }

        return initialNumUsages - numUsages;
    }

    /**
     * @return The number of pruned usages
     */
    public int prune(final int maxUsages, List<Usage> usages) {
        if (maxUsages <= 0) {
            throw new IllegalArgumentException("maxUsages must be greater than zero");
        }
        if (usages.size() < maxUsages) {
            return 0;
        }

        Random rnd = new Random(rndGenerator.nextLong());
        Collections.shuffle(usages, rnd);
        final int initialNumUsages = usages.size();
        for (int i = usages.size() - 1; i >= maxUsages; --i) {
            usages.remove(i);
        }

        return initialNumUsages - usages.size();
    }
}