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ASF GitHub Bot commented on FLINK-3477: --------------------------------------- Github user fhueske commented on a diff in the pull request: https://github.com/apache/flink/pull/1517#discussion_r64668546 --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/operators/chaining/ChainedReduceCombineDriver.java --- @@ -0,0 +1,305 @@ +/* + * 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.flink.runtime.operators.chaining; + +import org.apache.flink.api.common.functions.Function; +import org.apache.flink.api.common.functions.ReduceFunction; +import org.apache.flink.api.common.functions.util.FunctionUtils; +import org.apache.flink.api.common.typeutils.TypeComparator; +import org.apache.flink.api.common.typeutils.TypeSerializer; +import org.apache.flink.configuration.Configuration; +import org.apache.flink.core.memory.MemorySegment; +import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable; +import org.apache.flink.runtime.memory.MemoryManager; +import org.apache.flink.runtime.operators.BatchTask; +import org.apache.flink.runtime.operators.DriverStrategy; +import org.apache.flink.runtime.operators.hash.ReduceHashTable; +import org.apache.flink.runtime.operators.sort.FixedLengthRecordSorter; +import org.apache.flink.runtime.operators.sort.InMemorySorter; +import org.apache.flink.runtime.operators.sort.NormalizedKeySorter; +import org.apache.flink.runtime.operators.sort.QuickSort; +import org.apache.flink.util.Collector; +import org.apache.flink.util.MutableObjectIterator; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.io.EOFException; +import java.io.IOException; +import java.util.List; + +/** + * Chained version of ReduceCombineDriver. + */ +public class ChainedReduceCombineDriver<T> extends ChainedDriver<T, T> { + + private static final Logger LOG = LoggerFactory.getLogger(ChainedReduceCombineDriver.class); + + /** Fix length records with a length below this threshold will be in-place sorted, if possible. */ + private static final int THRESHOLD_FOR_IN_PLACE_SORTING = 32; + + + private AbstractInvokable parent; + + private TypeSerializer<T> serializer; + + private TypeComparator<T> comparator; + + private ReduceFunction<T> reducer; + + private DriverStrategy strategy; + + private InMemorySorter<T> sorter; + + private QuickSort sortAlgo = new QuickSort(); + + private ReduceHashTable<T> table; + + private List<MemorySegment> memory; + + private volatile boolean canceled; --- End diff -- Can we use `running` instead of `canceled` for the sake of consistency? > Add hash-based combine strategy for ReduceFunction > -------------------------------------------------- > > Key: FLINK-3477 > URL: https://issues.apache.org/jira/browse/FLINK-3477 > Project: Flink > Issue Type: Sub-task > Components: Local Runtime > Reporter: Fabian Hueske > Assignee: Gabor Gevay > > This issue is about adding a hash-based combine strategy for ReduceFunctions. > The interface of the {{reduce()}} method is as follows: > {code} > public T reduce(T v1, T v2) > {code} > Input type and output type are identical and the function returns only a > single value. A Reduce function is incrementally applied to compute a final > aggregated value. This allows to hold the preaggregated value in a hash-table > and update it with each function call. > The hash-based strategy requires special implementation of an in-memory hash > table. The hash table should support in place updates of elements (if the > updated value has the same size as the new value) but also appending updates > with invalidation of the old value (if the binary length of the new value > differs). The hash table needs to be able to evict and emit all elements if > it runs out-of-memory. > We should also add {{HASH}} and {{SORT}} compiler hints to > {{DataSet.reduce()}} and {{Grouping.reduce()}} to allow users to pick the > execution strategy. -- This message was sent by Atlassian JIRA (v6.3.4#6332)