Github user dbtsai commented on a diff in the pull request: https://github.com/apache/spark/pull/15628#discussion_r107785054 --- Diff: mllib-local/src/main/scala/org/apache/spark/ml/linalg/Matrices.scala --- @@ -161,6 +162,118 @@ sealed trait Matrix extends Serializable { */ @Since("2.0.0") def numActives: Int + + /** + * Converts this matrix to a sparse matrix. + * + * @param colMajor Whether the values of the resulting sparse matrix should be in column major + * or row major order. If `false`, resulting matrix will be row major. + */ + private[ml] def toSparseMatrix(colMajor: Boolean): SparseMatrix + + /** + * Converts this matrix to a sparse matrix in column major order. + */ + @Since("2.2.0") + def toSparseColMajor: SparseMatrix = toSparseMatrix(colMajor = true) + + /** + * Converts this matrix to a sparse matrix in row major order. + */ + @Since("2.2.0") + def toSparseRowMajor: SparseMatrix = toSparseMatrix(colMajor = false) + + /** + * Converts this matrix to a sparse matrix in column major order. + */ + @Since("2.2.0") + def toSparse: SparseMatrix = toSparseMatrix(colMajor = true) + + /** + * Converts this matrix to a dense matrix. + * + * @param colMajor Whether the values of the resulting dense matrix should be in column major + * or row major order. If `false`, resulting matrix will be row major. + */ + private[ml] def toDenseMatrix(colMajor: Boolean): DenseMatrix + + /** + * Converts this matrix to a dense matrix in column major order. + */ + @Since("2.2.0") + def toDense: DenseMatrix = toDenseMatrix(colMajor = true) + + /** + * Converts this matrix to a dense matrix in row major order. + */ + @Since("2.2.0") + def toDenseRowMajor: DenseMatrix = toDenseMatrix(colMajor = false) + + /** + * Converts this matrix to a dense matrix in column major order. + */ + @Since("2.2.0") + def toDenseColMajor: DenseMatrix = toDenseMatrix(colMajor = true) + + /** + * Returns a matrix in dense or sparse column major format, whichever uses less storage. + */ + @Since("2.2.0") + def compressedColMajor: Matrix = { + if (getDenseSizeInBytes < getSparseSizeInBytes(colMajor = true)) { + toDenseColMajor + } else { + toSparseColMajor + } + } + + /** + * Returns a matrix in dense or sparse row major format, whichever uses less storage. + */ + @Since("2.2.0") + def compressedRowMajor: Matrix = { + if (getDenseSizeInBytes < getSparseSizeInBytes(colMajor = false)) { + toDenseRowMajor + } else { + toSparseRowMajor + } + } + + /** + * Returns a matrix in dense column major, dense row major, sparse row major, or sparse column + * major format, whichever uses less storage. When dense representation is optimal, it maintains + * the current layout order. + */ + @Since("2.2.0") + def compressed: Matrix = { + val cscSize = getSparseSizeInBytes(colMajor = true) + val csrSize = getSparseSizeInBytes(colMajor = false) + if (getDenseSizeInBytes < math.min(cscSize, csrSize)) { + // dense matrix size is the same for column major and row major, so maintain current layout + toDenseMatrix(!isTransposed) --- End diff -- Call `toDense` if we decide to make `toDense` and `toSparse` outputting the same layout.
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