SPARK-4405 [MLLIB] Matrices.* construction methods should check for rows x cols overflow

Check that size of dense matrix array is not beyond Int.MaxValue in Matrices.* methods. jkbradley this should be an easy one. Review and/or merge as you see fit.

Author: Sean Owen <sowen@cloudera.com>

Closes #4461 from srowen/SPARK-4405 and squashes the following commits:

c67574e [Sean Owen] Check that size of dense matrix array is not beyond Int.MaxValue in Matrices.* methods

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

@@ -256,8 +256,11 @@ object DenseMatrix {
    * @param numCols number of columns of the matrix
    * @return `DenseMatrix` with size `numRows` x `numCols` and values of zeros
    */
-  def zeros(numRows: Int, numCols: Int): DenseMatrix =
+  def zeros(numRows: Int, numCols: Int): DenseMatrix = {
+    require(numRows.toLong * numCols <= Int.MaxValue,
+            s"$numRows x $numCols dense matrix is too large to allocate")
     new DenseMatrix(numRows, numCols, new Array[Double](numRows * numCols))
+  }
 
   /**
    * Generate a `DenseMatrix` consisting of ones.
@@ -265,8 +268,11 @@ object DenseMatrix {
    * @param numCols number of columns of the matrix
    * @return `DenseMatrix` with size `numRows` x `numCols` and values of ones
    */
-  def ones(numRows: Int, numCols: Int): DenseMatrix =
+  def ones(numRows: Int, numCols: Int): DenseMatrix = {
+    require(numRows.toLong * numCols <= Int.MaxValue,
+            s"$numRows x $numCols dense matrix is too large to allocate")
     new DenseMatrix(numRows, numCols, Array.fill(numRows * numCols)(1.0))
+  }
 
   /**
    * Generate an Identity Matrix in `DenseMatrix` format.
@@ -291,6 +297,8 @@ object DenseMatrix {
    * @return `DenseMatrix` with size `numRows` x `numCols` and values in U(0, 1)
    */
   def rand(numRows: Int, numCols: Int, rng: Random): DenseMatrix = {
+    require(numRows.toLong * numCols <= Int.MaxValue,
+            s"$numRows x $numCols dense matrix is too large to allocate")
     new DenseMatrix(numRows, numCols, Array.fill(numRows * numCols)(rng.nextDouble()))
   }
 
@@ -302,6 +310,8 @@ object DenseMatrix {
    * @return `DenseMatrix` with size `numRows` x `numCols` and values in N(0, 1)
    */
   def randn(numRows: Int, numCols: Int, rng: Random): DenseMatrix = {
+    require(numRows.toLong * numCols <= Int.MaxValue,
+            s"$numRows x $numCols dense matrix is too large to allocate")
     new DenseMatrix(numRows, numCols, Array.fill(numRows * numCols)(rng.nextGaussian()))
   }