[GitHub] [lucene-solr] jimczi commented on a change in pull request #1316: LUCENE-8929 parallel early termination in TopFieldCollector using minmin score

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jimczi commented on a change in pull request #1316: LUCENE-8929 parallel early termination in TopFieldCollector using minmin score
URL: https://github.com/apache/lucene-solr/pull/1316#discussion_r394215894
 
 

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 File path: lucene/core/src/java/org/apache/lucene/search/ParallelSortedCollector.java
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 @@ -0,0 +1,612 @@
+/*
+ * 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.
+ */
+package org.apache.lucene.search;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.PriorityQueue;
+
+import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.search.FieldValueHitQueue.Entry;
+import org.apache.lucene.search.TotalHits.Relation;
+
+/**
+ * A {@link Collector} for results sorted by field, optimized for early termination in
+ * the case where the {@link Sort} matches the index and the search is executed in parallel,
+ * using multiple threads.
+ *
+ * @lucene.experimental
+ */
+abstract class ParallelSortedCollector extends TopDocsCollector<Entry> {
+
+  private static final ScoreDoc[] EMPTY_SCOREDOCS = new ScoreDoc[0];
+
+  final int numHits;
+  final Sort sort;
+  final HitsThresholdChecker hitsThresholdChecker;
+  final FieldComparator<?> firstComparator;
+
+  // the current local minimum competitive score already propagated to the underlying scorer
+  float minCompetitiveScore;
+
+  // Enables global early termination with concurrent threads using minimum competitive scores and
+  // collected counts of all segments
+  final MaxScoreTerminator maxScoreTerminator;
+
+  final int numComparators;
+  FieldValueHitQueue.Entry bottom = null;
+  boolean queueFull;
+  int docBase;
+  final boolean needsScores;
+  final ScoreMode scoreMode;
+
+  // Declaring the constructor private prevents extending this class by anyone
+  // else. Note that the class cannot be final since it's extended by the
+  // internal versions. If someone will define a constructor with any other
+  // visibility, then anyone will be able to extend the class, which is not what
+  // we want.
+  private ParallelSortedCollector(FieldValueHitQueue<Entry> pq, int numHits, Sort sort,
+                                  HitsThresholdChecker hitsThresholdChecker, boolean needsScores,
+                                  MaxScoreTerminator maxScoreTerminator) {
+    super(pq);
+    this.needsScores = needsScores;
+    this.numHits = numHits;
+    this.sort = sort;
+    this.hitsThresholdChecker = hitsThresholdChecker;
+    this.maxScoreTerminator = maxScoreTerminator;
+    numComparators = pq.getComparators().length;
+    firstComparator = pq.getComparators()[0];
+    scoreMode = needsScores ? ScoreMode.COMPLETE : ScoreMode.COMPLETE_NO_SCORES;
+  }
+
+  private abstract class TopFieldLeafCollector implements LeafCollector {
+
+    final LeafFieldComparator comparator;
+    final int firstReverseMul;
+    final int reverseMul;
+    final LeafReaderContext context;
+    final MaxScoreTerminator.LeafState leafTerminationState;
+
+    private double score;
+    Scorable scorer;
+
+    TopFieldLeafCollector(FieldValueHitQueue<Entry> queue, LeafReaderContext context) throws IOException {
+      LeafFieldComparator[] comparators = queue.getComparators(context);
+      firstReverseMul = queue.reverseMul[0];
+      if (comparators.length == 1) {
+        this.reverseMul = queue.reverseMul[0];
+        this.comparator = comparators[0];
+      } else {
+        this.reverseMul = 1;
+        this.comparator = new MultiLeafFieldComparator(comparators, queue.reverseMul);
+      }
+      this.context = context;
+      leafTerminationState = maxScoreTerminator.addLeafState();
+    }
+
+    void countHit() {
+      ++totalHits;
+      // TODO: replace hitsThresholdChecker with something simpler
+      hitsThresholdChecker.incrementHitCount();
+    }
+
+    void collectHitIfCompetitive(int doc) throws IOException {
+      if (reverseMul * comparator.compareBottom(doc) > 0) {
 
 Review comment:
   if we specialize for parallel sorted  index we should get ride of this comparison ? A linked list should also be enough to keep track of the top N  per leave ?

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