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From GitBox <...@apache.org>
Subject [GitHub] sanha commented on a change in pull request #193: [NEMO-338] SkewSamplingPass
Date Tue, 19 Feb 2019 10:29:23 GMT
sanha commented on a change in pull request #193: [NEMO-338] SkewSamplingPass
URL: https://github.com/apache/incubator-nemo/pull/193#discussion_r257977037
 
 

 ##########
 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
 
 Review comment:
   Why do we need to sample P2?

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