Fanoid commented on code in PR #210:
URL: https://github.com/apache/flink-ml/pull/210#discussion_r1209634597


##########
flink-ml-lib/src/main/java/org/apache/flink/ml/common/gbt/GBTRunner.java:
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@@ -0,0 +1,304 @@
+/*
+ * 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.gbt;
+
+import org.apache.flink.api.common.functions.AggregateFunction;
+import org.apache.flink.api.common.functions.RichMapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.common.typeinfo.Types;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.iteration.DataStreamList;
+import org.apache.flink.iteration.IterationConfig;
+import org.apache.flink.iteration.Iterations;
+import org.apache.flink.iteration.ReplayableDataStreamList;
+import org.apache.flink.ml.classification.gbtclassifier.GBTClassifier;
+import org.apache.flink.ml.common.broadcast.BroadcastUtils;
+import org.apache.flink.ml.common.datastream.DataStreamUtils;
+import org.apache.flink.ml.common.datastream.TableUtils;
+import org.apache.flink.ml.common.gbt.defs.BoostingStrategy;
+import org.apache.flink.ml.common.gbt.defs.FeatureMeta;
+import org.apache.flink.ml.common.gbt.defs.LossType;
+import org.apache.flink.ml.common.gbt.defs.Node;
+import org.apache.flink.ml.common.gbt.defs.TaskType;
+import org.apache.flink.ml.common.gbt.defs.TrainContext;
+import org.apache.flink.ml.linalg.typeinfo.DenseVectorTypeInfo;
+import org.apache.flink.ml.linalg.typeinfo.SparseVectorTypeInfo;
+import org.apache.flink.ml.linalg.typeinfo.VectorTypeInfo;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.regression.gbtregressor.GBTRegressor;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import org.apache.flink.table.api.Table;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+import org.apache.flink.table.api.internal.TableImpl;
+import org.apache.flink.types.Row;
+import org.apache.flink.util.Preconditions;
+
+import org.apache.commons.lang3.ArrayUtils;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/** Runs a gradient boosting trees implementation. */
+public class GBTRunner {
+
+    private static boolean isVectorType(TypeInformation<?> typeInfo) {
+        return typeInfo instanceof DenseVectorTypeInfo
+                || typeInfo instanceof SparseVectorTypeInfo
+                || typeInfo instanceof VectorTypeInfo;
+    }
+
+    public static DataStream<GBTModelData> train(Table data, BaseGBTParams<?> 
estimator) {
+        String[] featuresCols = estimator.getFeaturesCols();
+        TypeInformation<?>[] featuresTypes =
+                Arrays.stream(featuresCols)
+                        .map(d -> 
TableUtils.getTypeInfoByName(data.getResolvedSchema(), d))
+                        .toArray(TypeInformation[]::new);
+        for (int i = 0; i < featuresCols.length; i += 1) {
+            Preconditions.checkArgument(
+                    null != featuresTypes[i],
+                    String.format(
+                            "Column name %s not existed in the input data.", 
featuresCols[i]));
+        }
+
+        boolean isInputVector = featuresCols.length == 1 && 
isVectorType(featuresTypes[0]);
+        return train(data, getStrategy(estimator, isInputVector));
+    }
+
+    /** Trains a gradient boosting tree model with given data and parameters. 
*/
+    static DataStream<GBTModelData> train(Table dataTable, BoostingStrategy 
strategy) {
+        StreamTableEnvironment tEnv =
+                (StreamTableEnvironment) ((TableImpl) 
dataTable).getTableEnvironment();
+        Tuple2<Table, DataStream<FeatureMeta>> preprocessResult =
+                strategy.isInputVector
+                        ? Preprocess.preprocessVecCol(dataTable, strategy)
+                        : Preprocess.preprocessCols(dataTable, strategy);
+        dataTable = preprocessResult.f0;
+        DataStream<FeatureMeta> featureMeta = preprocessResult.f1;
+
+        DataStream<Row> data = tEnv.toDataStream(dataTable);
+        DataStream<Tuple2<Double, Long>> labelSumCount =
+                DataStreamUtils.aggregate(data, new 
LabelSumCountFunction(strategy.labelCol));
+        return boost(dataTable, strategy, featureMeta, labelSumCount);
+    }
+
+    public static DataStream<Map<String, Double>> getFeatureImportance(
+            DataStream<GBTModelData> modelData) {
+        return modelData
+                .map(
+                        value -> {
+                            Map<Integer, Double> featureImportanceMap = new 
HashMap<>();
+                            double sum = 0.;
+                            for (List<Node> tree : value.allTrees) {
+                                for (Node node : tree) {
+                                    if (node.isLeaf) {
+                                        continue;
+                                    }
+                                    featureImportanceMap.merge(
+                                            node.split.featureId, 
node.split.gain, Double::sum);
+                                    sum += node.split.gain;
+                                }
+                            }
+                            if (sum > 0.) {
+                                for (Map.Entry<Integer, Double> entry :
+                                        featureImportanceMap.entrySet()) {
+                                    entry.setValue(entry.getValue() / sum);
+                                }
+                            }
+
+                            List<String> featureNames = value.featureNames;
+                            return featureImportanceMap.entrySet().stream()
+                                    .collect(
+                                            Collectors.toMap(
+                                                    d -> 
featureNames.get(d.getKey()),
+                                                    Map.Entry::getValue));
+                        })
+                .returns(Types.MAP(Types.STRING, Types.DOUBLE));
+    }
+
+    private static DataStream<GBTModelData> boost(
+            Table dataTable,
+            BoostingStrategy strategy,
+            DataStream<FeatureMeta> featureMeta,
+            DataStream<Tuple2<Double, Long>> labelSumCount) {
+        StreamTableEnvironment tEnv =
+                (StreamTableEnvironment) ((TableImpl) 
dataTable).getTableEnvironment();
+
+        final String featureMetaBcName = "featureMeta";
+        final String labelSumCountBcName = "labelSumCount";
+        Map<String, DataStream<?>> bcMap = new HashMap<>();
+        bcMap.put(featureMetaBcName, featureMeta);
+        bcMap.put(labelSumCountBcName, labelSumCount);
+
+        DataStream<TrainContext> initTrainContext =
+                BroadcastUtils.withBroadcastStream(
+                        Collections.singletonList(
+                                tEnv.toDataStream(tEnv.fromValues(0), 
Integer.class)),
+                        bcMap,
+                        (inputs) -> {
+                            //noinspection unchecked
+                            DataStream<Integer> input = (DataStream<Integer>) 
(inputs.get(0));
+                            return input.map(
+                                    new InitTrainContextFunction(
+                                            featureMetaBcName, 
labelSumCountBcName, strategy));
+                        });
+
+        DataStream<Row> data = tEnv.toDataStream(dataTable);
+        DataStreamList dataStreamList =
+                Iterations.iterateBoundedStreamsUntilTermination(
+                        DataStreamList.of(initTrainContext.broadcast()),

Review Comment:
   Thanks for your remind. I've moved the broadcast to iteration body.



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