[SPARK-4406] [MLib] FIX: Validate k in SVD

Raise exception when k is non-positive in SVD

Author: MechCoder <manojkumarsivaraj334@gmail.com>

Closes #3945 from MechCoder/spark-4406 and squashes the following commits:

64e6d2d [MechCoder] TST: Add better test errors and messages
12dae73 [MechCoder] [SPARK-4406] FIX: Validate k in SVD

mllib/src/main/scala/org/apache/spark/mllib/linalg/distributed/IndexedRowMatrix.scala

@@ -102,6 +102,9 @@ class IndexedRowMatrix(
       k: Int,
       computeU: Boolean = false,
       rCond: Double = 1e-9): SingularValueDecomposition[IndexedRowMatrix, Matrix] = {
+
+    val n = numCols().toInt
+    require(k > 0 && k <= n, s"Requested k singular values but got k=$k and numCols=$n.")
     val indices = rows.map(_.index)
     val svd = toRowMatrix().computeSVD(k, computeU, rCond)
     val U = if (computeU) {

mllib/src/main/scala/org/apache/spark/mllib/linalg/distributed/RowMatrix.scala

@@ -212,7 +212,7 @@ class RowMatrix(
       tol: Double,
       mode: String): SingularValueDecomposition[RowMatrix, Matrix] = {
     val n = numCols().toInt
-    require(k > 0 && k <= n, s"Request up to n singular values but got k=$k and n=$n.")
+    require(k > 0 && k <= n, s"Requested k singular values but got k=$k and numCols=$n.")
 
     object SVDMode extends Enumeration {
       val LocalARPACK, LocalLAPACK, DistARPACK = Value

mllib/src/test/scala/org/apache/spark/mllib/linalg/distributed/IndexedRowMatrixSuite.scala

@@ -113,6 +113,13 @@ class IndexedRowMatrixSuite extends FunSuite with MLlibTestSparkContext {
     assert(closeToZero(U * brzDiag(s) * V.t - localA))
   }
 
+  test("validate k in svd") {
+    val A = new IndexedRowMatrix(indexedRows)
+    intercept[IllegalArgumentException] {
+      A.computeSVD(-1)
+    }
+  }
+
   def closeToZero(G: BDM[Double]): Boolean = {
     G.valuesIterator.map(math.abs).sum < 1e-6
   }

mllib/src/test/scala/org/apache/spark/mllib/linalg/distributed/RowMatrixSuite.scala

@@ -171,6 +171,14 @@ class RowMatrixSuite extends FunSuite with MLlibTestSparkContext {
     }
   }
 
+  test("validate k in svd") {
+    for (mat <- Seq(denseMat, sparseMat)) {
+      intercept[IllegalArgumentException] {
+        mat.computeSVD(-1)
+      }
+    }
+  }
+
   def closeToZero(G: BDM[Double]): Boolean = {
     G.valuesIterator.map(math.abs).sum < 1e-6
   }