lindong28 commented on a change in pull request #28: URL: https://github.com/apache/flink-ml/pull/28#discussion_r761937399
########## File path: flink-ml-core/src/main/java/org/apache/flink/ml/common/datastream/DataStreamUtils.java ########## @@ -0,0 +1,243 @@ +/* + * 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.ml.common.datastream; + +import org.apache.flink.api.common.functions.MapPartitionFunction; +import org.apache.flink.api.common.state.ListState; +import org.apache.flink.api.common.state.ListStateDescriptor; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.common.typeutils.TypeComparator; +import org.apache.flink.api.java.typeutils.TypeExtractor; +import org.apache.flink.runtime.state.StateInitializationContext; +import org.apache.flink.runtime.state.StateSnapshotContext; +import org.apache.flink.streaming.api.datastream.DataStream; +import org.apache.flink.streaming.api.operators.AbstractStreamOperator; +import org.apache.flink.streaming.api.operators.BoundedOneInput; +import org.apache.flink.streaming.api.operators.OneInputStreamOperator; +import org.apache.flink.streaming.api.operators.TimestampedCollector; +import org.apache.flink.streaming.runtime.streamrecord.StreamRecord; + +import org.apache.commons.collections.IteratorUtils; + +import java.util.HashSet; +import java.util.List; +import java.util.Set; + +/** Provides utility functions for {@link DataStream}. */ +public class DataStreamUtils { + /** + * Applies allReduceSum on the input data stream. The input data stream is supposed to contain + * one double array in each partition. The result data stream has the same parallelism as the + * input, where each partition contains one double array that sums all of the double arrays in + * the input data stream. + * + * <p>Note that we throw exception when one of the following two cases happen: + * <li>There exists one partition that contains more than one double array. + * <li>The length of the double array is not consistent among all partitions. + * + * @param input The input data stream. + * @return The result data stream. + */ + public static DataStream<double[]> allReduceSum(DataStream<double[]> input) { + return AllReduceImpl.allReduceSum(input); + } + + /** + * Collects distinct values in a bounded data stream. The parallelism of the output stream is 1. + * + * @param <T> The class type of the input data stream. + * @param input The bounded input data stream. + * @return The result data stream that contains all the distinct values. + */ + public static <T> DataStream<T> distinct(DataStream<T> input) { + return input.transform( + "distinctInEachPartition", + input.getType(), + new DistinctPartitionOperator<>()) + .setParallelism(input.getParallelism()) + .transform( + "distinctInFinalPartition", + input.getType(), + new DistinctPartitionOperator<>()) + .setParallelism(1); + } + + /** + * Applies a {@link MapPartitionFunction} on a bounded data stream. + * + * @param input The input data stream. + * @param func The user defined mapPartition function. + * @param <IN> The class type of the input element. + * @param <OUT> The class type of output element. + * @return The result data stream. + */ + public static <IN, OUT> DataStream<OUT> mapPartition( + DataStream<IN> input, MapPartitionFunction<IN, OUT> func) { + TypeInformation<OUT> resultType = + TypeExtractor.getMapPartitionReturnTypes(func, input.getType(), null, true); + return input.transform("mapPartition", resultType, new MapPartitionOperator<>(func)) + .setParallelism(input.getParallelism()); + } + + /** + * Sorts the elements in each partition of the input bounded data stream. + * + * @param input The input data stream. + * @param comparator The comparator used to sort the elements. + * @param <IN> The class type of input element. + * @return The sorted data stream. + */ + public static <IN> DataStream<IN> sortPartition( + DataStream<IN> input, TypeComparator<IN> comparator) { + return input.transform( + "sortPartition", input.getType(), new SortPartitionOperator<>(comparator)) + .setParallelism(input.getParallelism()); Review comment: It is useful to know that `datastream.transform(...)` will change the output parallelism to `env. getParallelism(...)`. Thanks for the explanation. The question regarding why "we need to split the global partition (where all elements are sorted) to multiple partitions" still exists. We can discuss this when we add this method in the future. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@flink.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
