Github user yu-iskw commented on a diff in the pull request:
https://github.com/apache/spark/pull/8643#discussion_r43722360
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/api/python/LDAModelWrapper.scala ---
@@ -0,0 +1,45 @@
+/*
+ * 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.spark.mllib.api.python
+
+import scala.collection.JavaConverters
+
+import org.apache.spark.SparkContext
+import org.apache.spark.mllib.clustering.LDAModel
+import org.apache.spark.mllib.linalg.Matrix
+
+/**
+ * Wrapper around LDAModel to provide helper methods in Python
+ */
+private[python] class LDAModelWrapper(model: LDAModel) {
+
+ def topicsMatrix(): Matrix = model.topicsMatrix
+
+ def vocabSize(): Int = model.vocabSize
+
+ def describeTopics(): java.util.List[Array[Any]] =
describeTopics(this.model.vocabSize)
+
+ def describeTopics(maxTermsPerTopic: Int): java.util.List[Array[Any]] = {
+
+ val seq = model.describeTopics(maxTermsPerTopic).map { case (terms,
termWeights) =>
+ Array.empty[Any] ++ terms ++ termWeights
+ }.toSeq
+ JavaConverters.seqAsJavaListConverter(seq).asJava
--- End diff --
@davies thank you for tha comment. Could you please give me more
information about the type conversion?
How do we deserialize the return value in Python? Especially, I don't know
how to deserialize `scala.Tuple2` in Python. I tried to serialize the entire
list with `SerDe.dumps()` at `LDAModelWrapper.describeTopics()`, and then
confirm the return value in Python.
https://github.com/yu-iskw/spark/commit/54e5fda86ac3f3bac76b165615a0231d88a717aa
The testing result is as follow:
```
**********************************************************************
Failed example:
model.describeTopics()
Expected:
[([1, 0], [0.5..., 0.49...]), ([0, 1], [0.5..., 0.49...])]
Got:
({u'__class__': u'scala.Tuple2'}, {u'__class__': u'scala.Tuple2'})
```
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