[SPARK-4422][MLLIB]In some cases, Vectors.fromBreeze get wrong results.

cc mengxr

Author: GuoQiang Li <witgo@qq.com>

Closes #3281 from witgo/SPARK-4422 and squashes the following commits:

5f1fa5e [GuoQiang Li] import order
50783bd [GuoQiang Li] review commits
7a10123 [GuoQiang Li] In some cases, Vectors.fromBreeze get wrong results.

mllib/src/main/scala/org/apache/spark/mllib/linalg/Vectors.scala

@@ -237,7 +237,7 @@ object Vectors {
   private[mllib] def fromBreeze(breezeVector: BV[Double]): Vector = {
     breezeVector match {
       case v: BDV[Double] =>
-        if (v.offset == 0 && v.stride == 1) {
+        if (v.offset == 0 && v.stride == 1 && v.length == v.data.length) {
           new DenseVector(v.data)
         } else {
           new DenseVector(v.toArray)  // Can't use underlying array directly, so make a new one

mllib/src/test/scala/org/apache/spark/mllib/linalg/VectorsSuite.scala

@@ -17,6 +17,7 @@
 
 package org.apache.spark.mllib.linalg
 
+import breeze.linalg.{DenseMatrix => BDM}
 import org.scalatest.FunSuite
 
 import org.apache.spark.SparkException
@@ -166,4 +167,10 @@ class VectorsSuite extends FunSuite {
       assert(v === udt.deserialize(udt.serialize(v)))
     }
   }
+
+  test("fromBreeze") {
+    val x = BDM.zeros[Double](10, 10)
+    val v = Vectors.fromBreeze(x(::, 0))
+    assert(v.size === x.rows)
+  }
 }