perf.RandomFilter.java Source code

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Here is the source code for perf.RandomFilter.java

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package perf;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
import java.util.Random;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.DocIdSet;
import org.apache.lucene.search.Filter;
import org.apache.lucene.util.OpenBitSet;

class RandomFilter extends Filter {
    final double pctKeep;

    public RandomFilter(double pctKeep) {
        this.pctKeep = pctKeep;
    }

    @Override
    public DocIdSet getDocIdSet(IndexReader reader) {
        final Random rand = new Random(42);
        final int maxDoc = reader.maxDoc();
        OpenBitSet bits = new OpenBitSet(maxDoc);
        for (int docID = 0; docID < maxDoc; docID++) {
            if (rand.nextDouble() <= pctKeep) {
                bits.fastSet(docID);
            }
        }

        System.out.println("rfilt " + bits.cardinality());
        return bits;
    }
}