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From GitBox <...@apache.org>
Subject [GitHub] johnyangk commented on a change in pull request #193: [NEMO-338] SkewSamplingPass
Date Thu, 21 Feb 2019 05:19:38 GMT
johnyangk commented on a change in pull request #193: [NEMO-338] SkewSamplingPass
URL: https://github.com/apache/incubator-nemo/pull/193#discussion_r258782954
 
 

 ##########
 File path: compiler/optimizer/src/main/java/org/apache/nemo/compiler/optimizer/pass/compiletime/reshaping/SamplingSkewReshapingPass.java
 ##########
 @@ -0,0 +1,126 @@
+/*
+ * 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.nemo.compiler.optimizer.pass.compiletime.reshaping;
+
+import org.apache.nemo.common.KeyExtractor;
+import org.apache.nemo.common.dag.Edge;
+import org.apache.nemo.common.ir.IRDAG;
+import org.apache.nemo.common.ir.edge.IREdge;
+import org.apache.nemo.common.ir.edge.executionproperty.*;
+import org.apache.nemo.common.ir.vertex.IRVertex;
+import org.apache.nemo.common.ir.vertex.utility.MessageAggregatorVertex;
+import org.apache.nemo.common.ir.vertex.utility.MessageBarrierVertex;
+import org.apache.nemo.common.ir.vertex.utility.SamplingVertex;
+import org.apache.nemo.compiler.optimizer.pass.compiletime.Requires;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * Optimizes the PartitionSet property of shuffle edges to handle data skews using the SamplingVertex.
+ *
+ * This pass effectively partitions the IRDAG by non-oneToOne edges, clones each subDAG partition
using SamplingVertex
+ * to process sampled data, and executes each cloned partition prior to executing the corresponding
original partition.
+ *
+ * Suppose the IRDAG is partitioned into two sub-DAGs as follows:
+ * P1 - P2
+ *
+ * Then, this pass will produce something like:
+ * P1' - P1 - P2
+ *          - P2' - P2
+ * where Px' consists of SamplingVertex objects that clone the execution of Px.
+ *
+ * For each Px' this pass also inserts a MessageBarrierVertex, to use its data statistics
for dynamically optimizing
+ * the execution behaviors of Px.
+ */
+@Requires(CommunicationPatternProperty.class)
+public final class SamplingSkewReshapingPass extends ReshapingPass {
+  private static final Logger LOG = LoggerFactory.getLogger(SamplingSkewReshapingPass.class.getName());
+  private static final float SAMPLE_RATE = 0.1f;
+
+  /**
+   * Default constructor.
+   */
+  public SamplingSkewReshapingPass() {
+    super(SamplingSkewReshapingPass.class);
+  }
+
+  @Override
+  public IRDAG apply(final IRDAG dag) {
+    dag.topologicalDo(v -> {
+      for (final IREdge e : dag.getIncomingEdgesOf(v)) {
+        if (CommunicationPatternProperty.Value.Shuffle.equals(
+          e.getPropertyValue(CommunicationPatternProperty.class).get())) {
+          // Compute the partition and its source vertices
+          final IRVertex shuffleWriter = e.getSrc();
+          final Set<IRVertex> partitionAll = recursivelyBuildPartition(shuffleWriter,
dag);
+          final Set<IRVertex> partitionSources = partitionAll.stream().filter(vertexInPartition
->
+            !dag.getIncomingEdgesOf(vertexInPartition).stream()
+              .map(Edge::getSrc)
+              .anyMatch(partitionAll::contains)
+          ).collect(Collectors.toSet());
+
+          // Insert sampling vertices.
+          final Set<SamplingVertex> samplingVertices = partitionAll
+            .stream()
+            .map(vertexInPartition -> new SamplingVertex(vertexInPartition, SAMPLE_RATE))
+            .collect(Collectors.toSet());
+          dag.insert(samplingVertices, partitionSources);
+
+          // Insert the message vertex.
+          // We first obtain a clonedShuffleEdge to analyze the data statistics of the shuffle
outputs of
+          // the sampling vertex right before shuffle.
+          final SamplingVertex rightBeforeShuffle = samplingVertices.stream()
+            .filter(sv -> sv.getOriginalVertex().equals(e.getSrc()))
+            .findFirst()
+            .orElseThrow(() -> new IllegalStateException());
+          final IREdge clonedShuffleEdge = rightBeforeShuffle.getCloneOfOriginalEdge(e);
+
+          final KeyExtractor keyExtractor = e.getPropertyValue(KeyExtractorProperty.class).get();
 
 Review comment:
   Agreed. I've filed the JIRA: https://issues.apache.org/jira/browse/NEMO-343

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