mikemccand commented on a change in pull request #163:
URL: https://github.com/apache/lucene/pull/163#discussion_r643866949
##########
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:
> @bruno-roustant came up with some clever new hashing improvements
recently - these are not published as a public revision but you can get them
from the repository and compile it locally. See this for details:
>
> https://issues.carrot2.org/browse/HPPC-176
Whoa, this looks new "worm" hashing looks great! That is frequently a great
tradeoff (slower put, faster get)? Hmm why hasn't this been "published in a
public revision" yet :)
##########
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;
Review comment:
Hmm do we actually fall inside this `if`? I would think we shouldn't
ever hit this -- we should't call `freeze` unless something had in fact
changed? Or, if we are, something else might be wrong? Or maybe I am simply
confused ;)
##########
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() {
Review comment:
Yeah this is odd -- `+1` to make the hash code a privately maintained
thing.
##########
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:
> How many states are we manipulating? If it's not too many, then indeed
maybe a simple array of state-counters is enough?
> If array[i] is the counter for state i, then incr(i) / decr(i) are 0(1),
hash is still O(n) (skipping 0 values), freeze does not need to be sorted.
That's a neat idea!
The tricky thing is that these are usually very sparsely occupied sets (each
DFA state is "typically" just a few NFA states, I think), so we would have to
pay the O(N) cost to walk that array and turn it into the frozen (sparse
`int[]`) representation.
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