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Posted to issues@commons.apache.org by GitBox <gi...@apache.org> on 2022/07/13 12:23:02 UTC
[GitHub] [commons-collections] garydgregory commented on a diff in pull request #321: Adding IndexedLinkedList and its tests.
garydgregory commented on code in PR #321:
URL: https://github.com/apache/commons-collections/pull/321#discussion_r920010604
##########
src/main/java/org/apache/commons/collections4/list/IndexedLinkedList.java:
##########
@@ -0,0 +1,3460 @@
+/*
+ * 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 com.github.coderodde.util;
+
+import java.lang.reflect.Array;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.ConcurrentModificationException;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+import java.util.function.IntFunction;
+import java.util.function.Predicate;
+import java.util.function.UnaryOperator;
+
+/**
+ * <p>
+ * This class implements the indexed, heuristic doubly-linked list data
+ * structure that runs all the single-element operations in expected
+ * \(\mathcal{O}(\sqrt{n})\) time. Under the hood, the actual elements are
+ * stored in a doubly-linked list. However, we also maintain a list of so-called
+ * <i>"fingers"</i> stored in a random access array. Each finger {@code F}
+ * contains two data fields:
+ * <ul>
+ * <li>{@code F.node} - the actual element node,</li>
+ * <li>{@code F.index} - the appearance index of {@code F.node} in the actual
+ * list.</li>
+ * </ul>
+ *
+ * <p>
+ *
+ * For the list of size \(n\), we maintain
+ * \(\bigg \lceil \sqrt{n} \bigg \rceil + 1\) fingers. The rightmost finger in
+ * the finger list is a <i>special end-of-list sentinel</i>. It always has
+ * {@code F.node = null} and {@code F.index = } \(n\). The fingers are sorted by
+ * their indices. That arrangement allows simpler and faster code in the method
+ * that accesses a finger via element index; see
+ * {@link FingerList#getFingerIndexImpl(int)}. Since number of fingers is
+ * \(\sqrt{n}\), and assuming that the fingers are evenly distributed, each
+ * finger "covers" \(n / \sqrt{n} = \sqrt{n}\) elements. In order to access an
+ * element in the actual list, we first consult the finger list for the index
+ * {@code i} of the finger {@code fingerArray[i]} that is closest to the index
+ * of the target element. This runs in
+ *
+ * \[
+ * \mathcal{O}(\log \sqrt{n}) = \mathcal{O}(\log n^{1/2}) = \mathcal{O}(\frac{1}{2} \log n) = \mathcal{O}(\log n).
+ * \]
+ *
+ * The rest is to <i>"rewind"</i> the closest finger to point to the target
+ * element (which requires \(\mathcal{O}(\sqrt{n})\) on evenly distributed
+ * finger lis).
+ *
+ * @author Rodion "rodde" Efremov
+ * @version 1.61 (Sep 26, 2021)
+ * @since 1.6 (Sep 1, 2021)
+ */
+public class IndexedLinkedList<E> implements Deque<E>,
Review Comment:
This should fit in the rest of the framework by subclassing AbstractLinkedList
##########
src/main/java/org/apache/commons/collections4/list/IndexedLinkedList.java:
##########
@@ -0,0 +1,3460 @@
+/*
+ * 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 com.github.coderodde.util;
+
+import java.lang.reflect.Array;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.ConcurrentModificationException;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+import java.util.function.IntFunction;
+import java.util.function.Predicate;
+import java.util.function.UnaryOperator;
+
+/**
+ * <p>
+ * This class implements the indexed, heuristic doubly-linked list data
+ * structure that runs all the single-element operations in expected
+ * \(\mathcal{O}(\sqrt{n})\) time. Under the hood, the actual elements are
+ * stored in a doubly-linked list. However, we also maintain a list of so-called
+ * <i>"fingers"</i> stored in a random access array. Each finger {@code F}
+ * contains two data fields:
+ * <ul>
+ * <li>{@code F.node} - the actual element node,</li>
+ * <li>{@code F.index} - the appearance index of {@code F.node} in the actual
+ * list.</li>
+ * </ul>
+ *
+ * <p>
+ *
+ * For the list of size \(n\), we maintain
+ * \(\bigg \lceil \sqrt{n} \bigg \rceil + 1\) fingers. The rightmost finger in
+ * the finger list is a <i>special end-of-list sentinel</i>. It always has
+ * {@code F.node = null} and {@code F.index = } \(n\). The fingers are sorted by
+ * their indices. That arrangement allows simpler and faster code in the method
+ * that accesses a finger via element index; see
+ * {@link FingerList#getFingerIndexImpl(int)}. Since number of fingers is
+ * \(\sqrt{n}\), and assuming that the fingers are evenly distributed, each
+ * finger "covers" \(n / \sqrt{n} = \sqrt{n}\) elements. In order to access an
+ * element in the actual list, we first consult the finger list for the index
+ * {@code i} of the finger {@code fingerArray[i]} that is closest to the index
+ * of the target element. This runs in
+ *
+ * \[
+ * \mathcal{O}(\log \sqrt{n}) = \mathcal{O}(\log n^{1/2}) = \mathcal{O}(\frac{1}{2} \log n) = \mathcal{O}(\log n).
+ * \]
+ *
+ * The rest is to <i>"rewind"</i> the closest finger to point to the target
+ * element (which requires \(\mathcal{O}(\sqrt{n})\) on evenly distributed
+ * finger lis).
+ *
+ * @author Rodion "rodde" Efremov
+ * @version 1.61 (Sep 26, 2021)
+ * @since 1.6 (Sep 1, 2021)
Review Comment:
The next version of Collections is 4.5
##########
src/main/java/org/apache/commons/collections4/list/IndexedLinkedList.java:
##########
@@ -0,0 +1,3460 @@
+/*
+ * 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 com.github.coderodde.util;
+
+import java.lang.reflect.Array;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.ConcurrentModificationException;
+import java.util.Deque;
+import java.util.Iterator;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.Spliterator;
+import java.util.function.Consumer;
+import java.util.function.IntFunction;
+import java.util.function.Predicate;
+import java.util.function.UnaryOperator;
+
+/**
+ * <p>
+ * This class implements the indexed, heuristic doubly-linked list data
+ * structure that runs all the single-element operations in expected
+ * \(\mathcal{O}(\sqrt{n})\) time. Under the hood, the actual elements are
+ * stored in a doubly-linked list. However, we also maintain a list of so-called
+ * <i>"fingers"</i> stored in a random access array. Each finger {@code F}
+ * contains two data fields:
+ * <ul>
+ * <li>{@code F.node} - the actual element node,</li>
+ * <li>{@code F.index} - the appearance index of {@code F.node} in the actual
+ * list.</li>
+ * </ul>
+ *
+ * <p>
+ *
+ * For the list of size \(n\), we maintain
+ * \(\bigg \lceil \sqrt{n} \bigg \rceil + 1\) fingers. The rightmost finger in
+ * the finger list is a <i>special end-of-list sentinel</i>. It always has
+ * {@code F.node = null} and {@code F.index = } \(n\). The fingers are sorted by
+ * their indices. That arrangement allows simpler and faster code in the method
+ * that accesses a finger via element index; see
+ * {@link FingerList#getFingerIndexImpl(int)}. Since number of fingers is
+ * \(\sqrt{n}\), and assuming that the fingers are evenly distributed, each
+ * finger "covers" \(n / \sqrt{n} = \sqrt{n}\) elements. In order to access an
+ * element in the actual list, we first consult the finger list for the index
+ * {@code i} of the finger {@code fingerArray[i]} that is closest to the index
+ * of the target element. This runs in
+ *
+ * \[
+ * \mathcal{O}(\log \sqrt{n}) = \mathcal{O}(\log n^{1/2}) = \mathcal{O}(\frac{1}{2} \log n) = \mathcal{O}(\log n).
+ * \]
+ *
+ * The rest is to <i>"rewind"</i> the closest finger to point to the target
+ * element (which requires \(\mathcal{O}(\sqrt{n})\) on evenly distributed
+ * finger lis).
+ *
+ * @author Rodion "rodde" Efremov
Review Comment:
FYI, we do not use author tags. Attribution is usually done in changes.xml, and/or pom.xml.
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