[GitHub] [lucene] mikemccand commented on a change in pull request #163: LUCENE-9983: Stop sorting determinize powersets unnecessarily

[GitBox <gi...@apache.org>]

mikemccand commented on a change in pull request #163:
URL: https://github.com/apache/lucene/pull/163#discussion_r642695443



##########
File path: lucene/core/build.gradle
##########
@@ -20,6 +20,8 @@ apply plugin: 'java-library'
 description = 'Lucene core library'
 
 dependencies {
+  implementation 'com.carrotsearch:hppc'

Review comment:
       Can you add a `// nocommit` here?  We can't take (external) dependencies in Lucene's `core` ... but hopefully we can fork the one HPPC class we need here (`IntIntHashMap`?).

##########
File path: lucene/core/src/java/org/apache/lucene/util/automaton/StateSet.java
##########
@@ -0,0 +1,107 @@
+/*
+ * 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.util.automaton;
+
+import com.carrotsearch.hppc.BitMixer;
+import com.carrotsearch.hppc.IntIntHashMap;
+import com.carrotsearch.hppc.cursors.IntCursor;
+import java.util.Arrays;
+
+/** A thin wrapper of {@link com.carrotsearch.hppc.IntIntHashMap} */
+final class StateSet extends IntSet {
+
+  private final IntIntHashMap inner;
+  private int hashCode;

Review comment:
       @dweiss suggested upgrading the hash to `long` to further reduce chance of false collisions.

##########
File path: lucene/core/src/java/org/apache/lucene/util/automaton/StateSet.java
##########
@@ -0,0 +1,107 @@
+/*
+ * 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.util.automaton;
+
+import com.carrotsearch.hppc.BitMixer;
+import com.carrotsearch.hppc.IntIntHashMap;
+import com.carrotsearch.hppc.cursors.IntCursor;
+import java.util.Arrays;
+
+/** A thin wrapper of {@link com.carrotsearch.hppc.IntIntHashMap} */
+final class StateSet extends IntSet {
+
+  private final IntIntHashMap inner;
+  private int hashCode;
+  private boolean changed;
+  private int[] arrayCache = new int[0];
+
+  StateSet(int capacity) {
+    inner = new IntIntHashMap(capacity);
+  }
+
+  // Adds this state to the set
+  void incr(int num) {
+    if (inner.addTo(num, 1) == 1) {
+      changed = true;
+    }
+  }
+
+  // Removes this state from the set, if count decrs to 0
+  void decr(int num) {
+    assert inner.containsKey(num);
+    int keyIndex = inner.indexOf(num);
+    int count = inner.indexGet(keyIndex) - 1;
+    if (count == 0) {
+      inner.remove(num);
+      changed = true;
+    } else {
+      inner.indexReplace(keyIndex, count);
+    }
+  }
+
+  void computeHash() {
+    if (changed == false) {
+      return;
+    }
+    hashCode = inner.size();
+    for (IntCursor cursor : inner.keys()) {
+      hashCode += BitMixer.mix(cursor.value);
+    }
+  }
+
+  /**
+   * Create a snapshot of this int set associated with a given state. The snapshot will not retain
+   * any frequency information about the elements of this set, only existence.
+   *
+   * <p>It is the caller's responsibility to ensure that the hashCode and data are up to date via
+   * the {@link #computeHash()} method before calling this method.
+   *
+   * @param state the state to associate with the frozen set.
+   * @return A new FrozenIntSet with the same values as this set.
+   */
+  FrozenIntSet freeze(int state) {
+    if (changed == false) {
+      assert arrayCache != null;
+      return new FrozenIntSet(arrayCache, hashCode, state);
+    }
+    return new FrozenIntSet(getArray(), hashCode, state);
+  }
+
+  @Override
+  int[] getArray() {
+    if (changed == false) {
+      assert arrayCache != null;
+      return arrayCache;
+    }
+    changed = false;
+    arrayCache = inner.keys().toArray();
+    // we need to sort this array since "equals" method depend on this
+    Arrays.sort(arrayCache);

Review comment:
       Oh I see, we are still sorting on `freeze`, but not when accumulating the powerset.  Curious this is so much faster :)  I would expect it to be slower on the adversarial regexp, I think, because we pay the sort price on every freeze now, instead on insert/delete into this map?  Confusing :)




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