compress vectors in VectorAssembler

Author: mengxr

mllib/src/main/scala/org/apache/spark/ml/feature/VectorAssembler.scala

@@ -102,6 +102,6 @@ object VectorAssembler {
       case o =>
         throw new SparkException(s"$o of type ${o.getClass.getName} is not supported.")
     }
-    Vectors.sparse(cur, indices.result(), values.result())
+    Vectors.sparse(cur, indices.result(), values.result()).compressed
   }
 }

mllib/src/test/scala/org/apache/spark/ml/feature/VectorAssemblerSuite.scala

@@ -20,7 +20,7 @@ package org.apache.spark.ml.feature
 import org.scalatest.FunSuite
 
 import org.apache.spark.SparkException
-import org.apache.spark.mllib.linalg.{Vector, Vectors}
+import org.apache.spark.mllib.linalg.{DenseVector, SparseVector, Vector, Vectors}
 import org.apache.spark.mllib.util.MLlibTestSparkContext
 import org.apache.spark.sql.{Row, SQLContext}
 
@@ -48,6 +48,14 @@ class VectorAssemblerSuite extends FunSuite with MLlibTestSparkContext {
     }
   }
 
+  test("assemble should compress vectors") {
+    import org.apache.spark.ml.feature.VectorAssembler.assemble
+    val v1 = assemble(0.0, 0.0, 0.0, Vectors.dense(4.0))
+    assert(v1.isInstanceOf[SparseVector])
+    val v2 = assemble(1.0, 2.0, 3.0, Vectors.sparse(1, Array(0), Array(4.0)))
+    assert(v2.isInstanceOf[DenseVector])
+  }
+
   test("VectorAssembler") {
     val df = sqlContext.createDataFrame(Seq(
       (0, 0.0, Vectors.dense(1.0, 2.0), "a", Vectors.sparse(2, Array(1), Array(3.0)), 10L)