yunfengzhou-hub commented on a change in pull request #28:
URL: https://github.com/apache/flink-ml/pull/28#discussion_r753930171



##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/common/param/HasL2.java
##########
@@ -0,0 +1,42 @@
+/*
+ * 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.param;
+
+import org.apache.flink.ml.param.DoubleParam;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.param.ParamValidators;
+import org.apache.flink.ml.param.WithParams;
+
+/** Interface for the shared L2 regularization param. */
+public interface HasL2<T> extends WithParams<T> {
+    Param<Double> L_2 =
+            new DoubleParam(
+                    "l2",
+                    "The L2-regularized parameter. The default value is 0.",

Review comment:
       We might need to establish a unified practice of whether to describe the 
default value (or accepted values in enum params). We can discuss it offline.

##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/classification/linear/LogisticGradient.java
##########
@@ -0,0 +1,97 @@
+/*
+ * 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.classification.linear;
+
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.tuple.Tuple3;
+import org.apache.flink.ml.common.linalg.BLAS;
+
+import java.io.Serializable;
+
+/** Logistic gradient. */

Review comment:
       Shall we have a more detailed description for this class? It might be 
difficult to infer the functionality of this class by reading this javadoc.

##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/common/param/HasBatchSize.java
##########
@@ -0,0 +1,43 @@
+/*
+ * 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.param;
+
+import org.apache.flink.ml.param.IntParam;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.param.ParamValidators;
+import org.apache.flink.ml.param.WithParams;
+
+/** Interface for the shared batchSize param. */
+public interface HasBatchSize<T> extends WithParams<T> {
+
+    Param<Integer> BATCH_SIZE =
+            new IntParam(
+                    "batchSize",
+                    "batch size of training algorithms. The default value is 
100.",

Review comment:
       A better style would be make descriptions start with Uppercase letter 
and ends with full stop. 

##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/classification/linear/LogisticRegressionModel.java
##########
@@ -0,0 +1,220 @@
+/*
+ * 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.classification.linear;
+
+import org.apache.flink.api.common.eventtime.WatermarkStrategy;
+import org.apache.flink.api.common.functions.RichMapFunction;
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.PrimitiveArrayTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.connector.source.Source;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.typeutils.RowTypeInfo;
+import org.apache.flink.connector.file.sink.FileSink;
+import org.apache.flink.connector.file.src.FileSource;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.ml.api.core.Model;
+import 
org.apache.flink.ml.classification.linear.LogisticRegressionModelData.LogisticRegressionModelDataEncoder;
+import 
org.apache.flink.ml.classification.linear.LogisticRegressionModelData.LogisticRegressionModelDataStreamFormat;
+import org.apache.flink.ml.common.broadcast.BroadcastUtils;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.util.ParamUtils;
+import org.apache.flink.ml.util.ReadWriteUtils;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import 
org.apache.flink.streaming.api.functions.sink.filesystem.bucketassigners.BasePathBucketAssigner;
+import 
org.apache.flink.streaming.api.functions.sink.filesystem.rollingpolicies.OnCheckpointRollingPolicy;
+import org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator;
+import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+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 java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/** This class implements {@link Model} for {@link LogisticRegression}. */
+public class LogisticRegressionModel
+        implements Model<LogisticRegressionModel>,
+                LogisticRegressionModelParams<LogisticRegressionModel> {
+
+    private Map<Param<?>, Object> paramMap;
+
+    private Table model;
+
+    public LogisticRegressionModel(Map<Param<?>, Object> paramMap) {
+        this.paramMap = paramMap;
+        ParamUtils.initializeMapWithDefaultValues(this.paramMap, this);
+    }
+
+    public LogisticRegressionModel() {
+        this(new HashMap<>());

Review comment:
       Maybe the default constructor should be implemented like in `Kmeans`?
   
   ```
   ParamUtils.initializeMapWithDefaultValues(paramMap, this);
   ```

##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/common/param/HasEpsilon.java
##########
@@ -0,0 +1,43 @@
+/*
+ * 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.param;
+
+import org.apache.flink.ml.param.DoubleParam;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.param.ParamValidators;
+import org.apache.flink.ml.param.WithParams;
+
+/** Interface for the shared epsilon param. */
+public interface HasEpsilon<T> extends WithParams<T> {
+
+    Param<Double> EPSILON =
+            new DoubleParam(
+                    "epsilon",
+                    "Convergence tolerance for iterative algorithms. The 
default value is 0.1",
+                    0.1,

Review comment:
       Shall we make the default value same as either both Alink `HasEpsilon` 
or Spark `HasTol`? I think it could be better to adopt one of the existing 
practices.

##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/classification/linear/LogisticRegressionModel.java
##########
@@ -0,0 +1,220 @@
+/*
+ * 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.classification.linear;
+
+import org.apache.flink.api.common.eventtime.WatermarkStrategy;
+import org.apache.flink.api.common.functions.RichMapFunction;
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.PrimitiveArrayTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.connector.source.Source;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.typeutils.RowTypeInfo;
+import org.apache.flink.connector.file.sink.FileSink;
+import org.apache.flink.connector.file.src.FileSource;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.ml.api.core.Model;
+import 
org.apache.flink.ml.classification.linear.LogisticRegressionModelData.LogisticRegressionModelDataEncoder;
+import 
org.apache.flink.ml.classification.linear.LogisticRegressionModelData.LogisticRegressionModelDataStreamFormat;
+import org.apache.flink.ml.common.broadcast.BroadcastUtils;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.util.ParamUtils;
+import org.apache.flink.ml.util.ReadWriteUtils;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import 
org.apache.flink.streaming.api.functions.sink.filesystem.bucketassigners.BasePathBucketAssigner;
+import 
org.apache.flink.streaming.api.functions.sink.filesystem.rollingpolicies.OnCheckpointRollingPolicy;
+import org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator;
+import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+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 java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+/** This class implements {@link Model} for {@link LogisticRegression}. */
+public class LogisticRegressionModel
+        implements Model<LogisticRegressionModel>,
+                LogisticRegressionModelParams<LogisticRegressionModel> {
+
+    private Map<Param<?>, Object> paramMap;
+
+    private Table model;
+
+    public LogisticRegressionModel(Map<Param<?>, Object> paramMap) {
+        this.paramMap = paramMap;
+        ParamUtils.initializeMapWithDefaultValues(this.paramMap, this);
+    }
+
+    public LogisticRegressionModel() {
+        this(new HashMap<>());
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        StreamTableEnvironment tEnv =
+                (StreamTableEnvironment) ((TableImpl) 
model).getTableEnvironment();
+        String dataPath = ReadWriteUtils.getDataPath(path);
+        FileSink<LogisticRegressionModelData> sink =
+                FileSink.forRowFormat(new Path(dataPath), new 
LogisticRegressionModelDataEncoder())
+                        .withRollingPolicy(OnCheckpointRollingPolicy.build())
+                        .withBucketAssigner(new BasePathBucketAssigner<>())
+                        .build();
+        ReadWriteUtils.saveMetadata(this, path);
+        tEnv.toDataStream(model)
+                .map(x -> (LogisticRegressionModelData) x.getField(0))
+                .sinkTo(sink)
+                .setParallelism(1);
+    }
+
+    public static LogisticRegressionModel load(StreamExecutionEnvironment env, 
String path)
+            throws IOException {
+        StreamTableEnvironment tEnv = StreamTableEnvironment.create(env);
+        Source<LogisticRegressionModelData, ?, ?> source =
+                FileSource.forRecordStreamFormat(
+                                new LogisticRegressionModelDataStreamFormat(),
+                                ReadWriteUtils.getDataPaths(path))
+                        .build();
+        LogisticRegressionModel model = ReadWriteUtils.loadStageParam(path);
+        DataStream<LogisticRegressionModelData> modelData =
+                env.fromSource(source, WatermarkStrategy.noWatermarks(), 
"modelData");
+        model.setModelData(tEnv.fromDataStream(modelData));
+        return model;
+    }
+
+    @Override
+    public LogisticRegressionModel setModelData(Table... inputs) {
+        model = inputs[0];
+        return this;
+    }
+
+    @Override
+    public Table[] getModelData() {
+        return new Table[] {model};
+    }
+
+    @Override
+    public Table[] transform(Table... inputs) {
+        StreamTableEnvironment tEnv =
+                (StreamTableEnvironment) ((TableImpl) 
inputs[0]).getTableEnvironment();
+
+        DataStream<Row> data = tEnv.toDataStream(inputs[0]);
+        final String broadcastModelName = "broadcastModel";
+        DataStream<LogisticRegressionModelData> modelData =
+                tEnv.toDataStream(model).map(x -> 
(LogisticRegressionModelData) x.getField(0));
+        DataStream<Row> predictResult =
+                BroadcastUtils.withBroadcastStream(
+                        Collections.singletonList(data),
+                        Collections.singletonMap(broadcastModelName, 
modelData),
+                        inputList -> {
+                            DataStream inputData = inputList.get(0);
+                            return inputData.transform(
+                                    "predict",
+                                    new RowTypeInfo(
+                                            new TypeInformation[] {
+                                                PrimitiveArrayTypeInfo
+                                                        
.DOUBLE_PRIMITIVE_ARRAY_TYPE_INFO,
+                                                BasicTypeInfo.DOUBLE_TYPE_INFO,
+                                                PrimitiveArrayTypeInfo
+                                                        
.DOUBLE_PRIMITIVE_ARRAY_TYPE_INFO
+                                            },
+                                            new String[] {
+                                                getFeaturesCol(),
+                                                getPredictionCol(),
+                                                getPredictionDetailCol()
+                                            }),
+                                    new PredictOp(
+                                            new PredictOneRecord(
+                                                    getFeaturesCol(), 
broadcastModelName)));
+                        });
+
+        return new Table[] {tEnv.fromDataStream(predictResult)};
+    }
+
+    /** A utility operator used for prediction. */
+    private static class PredictOp extends AbstractUdfStreamOperator<Row, 
RichMapFunction<Row, Row>>
+            implements OneInputStreamOperator<Row, Row> {
+        public PredictOp(RichMapFunction<Row, Row> userFunction) {
+            super(userFunction);
+        }
+
+        @Override
+        public void processElement(StreamRecord<Row> streamRecord) throws 
Exception {
+            output.collect(new 
StreamRecord<>(userFunction.map(streamRecord.getValue())));
+        }
+    }
+
+    /** A utility function used to predict one input record. */
+    private static class PredictOneRecord extends RichMapFunction<Row, Row> {
+
+        String broadcastModelName;
+

Review comment:
       It might be better to reduce the empty lines here.

##########
File path: 
flink-ml-lib/src/main/java/org/apache/flink/ml/classification/linear/LogisticRegression.java
##########
@@ -0,0 +1,594 @@
+/*
+ * 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.classification.linear;
+
+import org.apache.flink.api.common.functions.FlatMapFunction;
+import org.apache.flink.api.common.functions.RichMapFunction;
+import org.apache.flink.api.common.state.ListState;
+import org.apache.flink.api.common.state.ListStateDescriptor;
+import org.apache.flink.api.common.typeinfo.BasicTypeInfo;
+import org.apache.flink.api.common.typeinfo.PrimitiveArrayTypeInfo;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.tuple.Tuple3;
+import org.apache.flink.api.java.typeutils.TupleTypeInfo;
+import org.apache.flink.iteration.DataStreamList;
+import org.apache.flink.iteration.IterationBody;
+import org.apache.flink.iteration.IterationBodyResult;
+import org.apache.flink.iteration.IterationConfig;
+import org.apache.flink.iteration.IterationConfig.OperatorLifeCycle;
+import org.apache.flink.iteration.IterationListener;
+import org.apache.flink.iteration.Iterations;
+import org.apache.flink.iteration.ReplayableDataStreamList;
+import org.apache.flink.iteration.operator.OperatorStateUtils;
+import org.apache.flink.ml.api.core.Estimator;
+import org.apache.flink.ml.common.broadcast.BroadcastUtils;
+import org.apache.flink.ml.common.datastream.AllReduceUtils;
+import org.apache.flink.ml.common.datastream.DataStreamUtils;
+import org.apache.flink.ml.common.linalg.BLAS;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.util.ParamUtils;
+import org.apache.flink.ml.util.ReadWriteUtils;
+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.datastream.SingleOutputStreamOperator;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.streaming.api.operators.AbstractStreamOperator;
+import org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator;
+import org.apache.flink.streaming.api.operators.BoundedMultiInput;
+import org.apache.flink.streaming.api.operators.BoundedOneInput;
+import org.apache.flink.streaming.api.operators.OneInputStreamOperator;
+import org.apache.flink.streaming.api.operators.TwoInputStreamOperator;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+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.util.Collector;
+import org.apache.flink.util.OutputTag;
+import org.apache.flink.util.Preconditions;
+
+import org.apache.commons.collections.IteratorUtils;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+
+/** This class implements methods to train a logistic regression model. */
+public class LogisticRegression
+        implements Estimator<LogisticRegression, LogisticRegressionModel>,
+                LogisticRegressionParams<LogisticRegression> {
+
+    Map<Param<?>, Object> paramMap;
+
+    private static final OutputTag<Tuple2<double[], double[]>> MODEL_OUTPUT =
+            new OutputTag<Tuple2<double[], double[]>>("MODEL_OUTPUT") {};
+
+    public LogisticRegression(Map<Param<?>, Object> paramMap) {
+        this.paramMap = paramMap;
+        ParamUtils.initializeMapWithDefaultValues(this.paramMap, this);
+    }
+
+    public LogisticRegression() {
+        this(new HashMap<>());
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static LogisticRegression load(StreamExecutionEnvironment env, 
String path)
+            throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public LogisticRegressionModel fit(Table... inputs) {
+        Preconditions.checkArgument(inputs.length == 1);
+        StreamTableEnvironment tEnv =
+                (StreamTableEnvironment) ((TableImpl) 
inputs[0]).getTableEnvironment();
+
+        DataStream<Tuple3<Double, Double, double[]>> trainData =
+                tEnv.toDataStream(inputs[0])
+                        .map(
+                                row ->
+                                        Tuple3.of(
+                                                getWeightCol() == null
+                                                        ? new Double(1.0)
+                                                        : (Double) 
row.getField(getWeightCol()),
+                                                (Double) 
row.getField(getLabelCol()),
+                                                (double[]) 
row.getField(getFeaturesCol())))
+                        .returns(
+                                new TupleTypeInfo<>(
+                                        BasicTypeInfo.DOUBLE_TYPE_INFO,
+                                        BasicTypeInfo.DOUBLE_TYPE_INFO,
+                                        
PrimitiveArrayTypeInfo.DOUBLE_PRIMITIVE_ARRAY_TYPE_INFO));
+
+        DataStream<Double> labelValues = 
DataStreamUtils.distinct(trainData.map(x -> x.f1));
+
+        final String broadcastLabelsName = "broadcastLabels";
+        trainData =
+                BroadcastUtils.withBroadcastStream(
+                        Collections.singletonList(trainData),
+                        Collections.singletonMap(broadcastLabelsName, 
labelValues),
+                        inputList -> {
+                            DataStream data = inputList.get(0);
+                            return data.transform(
+                                    "preprocess",
+                                    new TupleTypeInfo<>(
+                                            BasicTypeInfo.DOUBLE_TYPE_INFO,
+                                            BasicTypeInfo.DOUBLE_TYPE_INFO,
+                                            
TypeInformation.of(double[].class)),
+                                    new PreprocessDataOp(
+                                            new 
PreprocessOneRecord(broadcastLabelsName)));
+                        });
+
+        DataStream<double[]> initModel =
+                trainData
+                        .transform(
+                                "getInitModel",
+                                TypeInformation.of(double[].class),
+                                new GetInitModel())
+                        .returns(TypeInformation.of(double[].class));
+
+        DataStream<Tuple2<double[], double[]>> modelAndLossCurve = 
train(trainData, initModel);
+
+        DataStream<LogisticRegressionModelData> modelData =
+                modelAndLossCurve
+                        .connect(labelValues)
+                        .transform(
+                                "composeModelData",
+                                
TypeInformation.of(LogisticRegressionModelData.class),
+                                new ComposeModelDataOp())
+                        .setParallelism(1);
+
+        LogisticRegressionModel model =
+                new LogisticRegressionModel(new HashMap<>())
+                        .setModelData(tEnv.fromDataStream(modelData));
+        ReadWriteUtils.updateExistingParams(model, paramMap);
+        return model;
+    }
+
+    /** Pre-processes the training data. */
+    private static class PreprocessDataOp
+            extends AbstractUdfStreamOperator<
+                    Tuple3<Double, Double, double[]>,
+                    RichMapFunction<
+                            Tuple3<Double, Double, double[]>, Tuple3<Double, 
Double, double[]>>>
+            implements OneInputStreamOperator<
+                    Tuple3<Double, Double, double[]>, Tuple3<Double, Double, 
double[]>> {
+        public PreprocessDataOp(
+                RichMapFunction<Tuple3<Double, Double, double[]>, 
Tuple3<Double, Double, double[]>>
+                        userFunction) {
+            super(userFunction);
+        }
+
+        @Override
+        public void processElement(StreamRecord<Tuple3<Double, Double, 
double[]>> streamRecord)
+                throws Exception {
+            streamRecord.replace(userFunction.map(streamRecord.getValue()));
+            output.collect(streamRecord);
+        }
+    }
+
+    /** Pre-processes the training data. */
+    private static class PreprocessOneRecord
+            extends RichMapFunction<
+                    Tuple3<Double, Double, double[]>, Tuple3<Double, Double, 
double[]>> {
+
+        String broadcastName;
+        double[] labelValues;
+
+        public PreprocessOneRecord(String broadcastName) {
+            this.broadcastName = broadcastName;
+        }
+
+        @Override
+        public Tuple3<Double, Double, double[]> map(Tuple3<Double, Double, 
double[]> value) {
+            if (labelValues == null) {
+                List<Double> labelList = 
getRuntimeContext().getBroadcastVariable(broadcastName);
+                labelValues = 
labelList.stream().mapToDouble(Double::doubleValue).toArray();
+            }
+            value.f1 = getLabel(labelValues, value.f1);
+            return value;
+        }
+
+        private double getLabel(double[] labels, double label) {
+            if (Math.abs(label - labels[0]) < 1e-7) {
+                return 1.;
+            } else {
+                return -1.;
+            }
+        }
+    }
+
+    /**
+     * Gets initialized model, note that the parallelism is same as the input 
train data, not one.
+     */
+    private static class GetInitModel extends AbstractStreamOperator<double[]>
+            implements OneInputStreamOperator<Tuple3<Double, Double, 
double[]>, double[]>,
+                    BoundedOneInput {
+
+        int dim = 0;
+
+        @Override
+        public void endInput() {
+            output.collect(new StreamRecord<>(new double[dim]));
+        }
+
+        @Override
+        public void processElement(StreamRecord<Tuple3<Double, Double, 
double[]>> streamRecord) {
+            dim = Math.max(dim, streamRecord.getValue().f2.length);
+        }
+    }
+
+    /**
+     * Trains a machine learning model on the input data and initialized 
model, return the trained
+     * model and loss curve.
+     *
+     * @param trainData the training data
+     * @param initModel the init model
+     * @return the trained model and loss during the training
+     */
+    private DataStream<Tuple2<double[], double[]>> train(
+            DataStream<Tuple3<Double, Double, double[]>> trainData,
+            DataStream<double[]> initModel) {
+        LogisticGradient logisticGradient = new LogisticGradient(getL2());
+
+        DataStreamList resultList =
+                Iterations.iterateBoundedStreamsUntilTermination(
+                        DataStreamList.of(initModel),
+                        ReplayableDataStreamList.notReplay(trainData),
+                        IterationConfig.newBuilder()
+                                
.setOperatorLifeCycle(OperatorLifeCycle.ALL_ROUND)
+                                .build(),
+                        new TrainIterationBody(
+                                logisticGradient,
+                                getBatchSize(),
+                                getLearningRate(),
+                                getMaxIter(),
+                                getEpsilon()));
+
+        return resultList.get(0);
+    }
+
+    /** The iteration implementation for training process. */
+    private static class TrainIterationBody implements IterationBody {
+
+        private final LogisticGradient logisticGradient;
+
+        private final int batchSize;
+
+        private final double learningRate;
+
+        private final int maxIter;
+
+        private final double epsilon;
+
+        public TrainIterationBody(
+                LogisticGradient logisticGradient,
+                int batchSize,
+                double learningRate,
+                int maxIter,
+                double epsilon) {
+            this.logisticGradient = logisticGradient;
+            this.batchSize = batchSize;
+            this.learningRate = learningRate;
+            this.maxIter = maxIter;
+            this.epsilon = epsilon;
+        }
+
+        @Override
+        public IterationBodyResult process(
+                DataStreamList variableStreams, DataStreamList dataStreams) {
+            DataStream<double[]> initModelOrGradientsAndWeightAndLoss = 
variableStreams.get(0);
+            DataStream<Tuple3<Double, Double, double[]>> trainData = 
dataStreams.get(0);
+            SingleOutputStreamOperator<double[]> gradientAndWeightAndLoss =
+                    trainData
+                            .connect(initModelOrGradientsAndWeightAndLoss)
+                            .transform(
+                                    "updateModelAndComputeGradients",
+                                    TypeInformation.of(double[].class),
+                                    new 
CacheDataAndUpdateModelAndComputeGradient(
+                                            logisticGradient,
+                                            batchSize,
+                                            learningRate,
+                                            maxIter,
+                                            epsilon));
+
+            DataStreamList outputs =
+                    IterationBody.forEachRound(
+                            DataStreamList.of(gradientAndWeightAndLoss),
+                            input -> {
+                                DataStream<double[]> feedback =
+                                        AllReduceUtils.allReduce(input.get(0));
+                                return DataStreamList.of(feedback);
+                            });
+            DataStream<Integer> terminatation =

Review comment:
       a small typo here.




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