Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/2451#discussion_r17800687
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
---
@@ -37,11 +44,197 @@ trait Matrix extends Serializable {
private[mllib] def toBreeze: BM[Double]
/** Gets the (i, j)-th element. */
- private[mllib] def apply(i: Int, j: Int): Double = toBreeze(i, j)
+ private[mllib] def apply(i: Int, j: Int): Double
+
+ /** Return the index for the (i, j)-th element in the backing array. */
+ private[mllib] def index(i: Int, j: Int): Int
+
+ /** Update element at (i, j) */
+ private[mllib] def update(i: Int, j: Int, v: Double): Unit
+
+ /** Get a deep copy of the matrix. */
+ def copy: Matrix
+ /** Convenience method for `Matrix`-`Matrix` multiplication.
+ * Note: `SparseMatrix`-`SparseMatrix` multiplication is not supported
*/
+ def multiply(y: Matrix): DenseMatrix = {
+ val C: DenseMatrix = DenseMatrix.zeros(numRows, y.numCols)
+ BLAS.gemm(false, false, 1.0, this, y, 0.0, C)
+ C
+ }
+
+ /** Convenience method for `Matrix`-`DenseVector` multiplication. */
+ def multiply(y: DenseVector): DenseVector = {
+ val output = new DenseVector(new Array[Double](numRows))
+ BLAS.gemv(1.0, this, y, 0.0, output)
+ output
+ }
+
+ /** Convenience method for `Matrix`^T^-`Matrix` multiplication.
+ * Note: `SparseMatrix`-`SparseMatrix` multiplication is not supported
*/
+ def transposeMultiply(y: Matrix): DenseMatrix = {
--- End diff --
How hard would it be to have matrices store a transpose bit indicated if
they are transposed (without the data being moved)? I envision:
* transpose() function which sets this bit (so transpose is a lazy
operation)
* eliminate transposeMultiply
* perhaps include a transposePhysical or tranpose(physical: Boolean) method
which forces data movement
I'm also OK with adding that support later on.
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