Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/3319#discussion_r22120299
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
---
@@ -197,6 +335,167 @@ class SparseMatrix(
}
override def copy = new SparseMatrix(numRows, numCols, colPtrs,
rowIndices, values.clone())
+
+ private[mllib] def map(f: Double => Double) =
+ new SparseMatrix(numRows, numCols, colPtrs, rowIndices, values.map(f))
+
+ private[mllib] def update(f: Double => Double): SparseMatrix = {
+ val len = values.length
+ var i = 0
+ while (i < len) {
+ values(i) = f(values(i))
+ i += 1
+ }
+ this
+ }
+
+ /** Generate a `DenseMatrix` from the given `SparseMatrix`. */
+ def toDense(): DenseMatrix = {
+ new DenseMatrix(numRows, numCols, toArray)
+ }
+}
+
+/**
+ * Factory methods for [[org.apache.spark.mllib.linalg.SparseMatrix]].
+ */
+object SparseMatrix {
+
+ /**
+ * Generate a `SparseMatrix` from Coordinate List (COO) format. Input
must be an array of
+ * (row, column, value) tuples.
+ * @param numRows number of rows of the matrix
+ * @param numCols number of columns of the matrix
+ * @param entries Array of (row, column, value) tuples
+ * @return The corresponding `SparseMatrix`
+ */
+ def fromCOO(numRows: Int, numCols: Int, entries: Array[(Int, Int,
Double)]): SparseMatrix = {
+ val sortedEntries = entries.sortBy(v => (v._2, v._1))
+ val colPtrs = new Array[Int](numCols + 1)
+ var nnz = 0
+ var lastCol = -1
+ val values = sortedEntries.map { case (i, j, v) =>
+ while (j != lastCol) {
+ colPtrs(lastCol + 1) = nnz
+ lastCol += 1
+ }
+ nnz += 1
+ v
+ }
+ while (numCols > lastCol) {
+ colPtrs(lastCol + 1) = nnz
+ lastCol += 1
+ }
+ new SparseMatrix(numRows, numCols, colPtrs.toArray,
sortedEntries.map(_._1), values)
+ }
+
+ /**
+ * Generate an Identity Matrix in `SparseMatrix` format.
+ * @param n number of rows and columns of the matrix
+ * @return `SparseMatrix` with size `n` x `n` and values of ones on the
diagonal
+ */
+ def speye(n: Int): SparseMatrix = {
+ new SparseMatrix(n, n, (0 to n).toArray, (0 until n).toArray,
Array.fill(n)(1.0))
+ }
+
+ /** Generates a `SparseMatrix` with a given random number generator and
`method`, which
+ * specifies the distribution. */
+ private def genRandMatrix(
+ numRows: Int,
+ numCols: Int,
+ density: Double,
+ rng: Random,
+ method: Random => Double): SparseMatrix = {
+ require(density >= 0.0 && density <= 1.0, "density must be a double in
the range " +
+ s"0.0 <= d <= 1.0. Currently, density: $density")
+ val length = math.ceil(numRows * numCols * density).toInt
+ val entries = MutableMap[(Int, Int), Double]()
+ var i = 0
+ if (density == 0.0) {
+ return new SparseMatrix(numRows, numCols, new Array[Int](numCols +
1),
+ Array[Int](), Array[Double]())
+ } else if (density == 1.0) {
+ return new SparseMatrix(numRows, numCols, (0 to numRows * numCols by
numRows).toArray,
+ (0 until numRows * numCols).toArray, Array.fill(numRows *
numCols)(method(rng)))
+ }
+ // Expected number of iterations is less than 1.5 * length
+ if (density < 0.34) {
+ while (i < length) {
+ var rowIndex = rng.nextInt(numRows)
+ var colIndex = rng.nextInt(numCols)
+ while (entries.contains((rowIndex, colIndex))) {
+ rowIndex = rng.nextInt(numRows)
+ colIndex = rng.nextInt(numCols)
+ }
+ entries += (rowIndex, colIndex) -> method(rng)
+ i += 1
+ }
+ } else { // selection - rejection method
+ var j = 0
+ val pool = numRows * numCols
+ // loop over columns so that the sort in fromCOO requires less
sorting
+ while (i < length && j < numCols) {
+ var passedInPool = j * numRows
+ var r = 0
+ while (i < length && r < numRows) {
+ if (rng.nextDouble() < 1.0 * (length - i) / (pool -
passedInPool)) {
+ entries += (r, j) -> method(rng)
--- End diff --
Using a map here is not optimal. The sampled entries are ordered. We can
construct `rowIndices` and `colPtrs` directly.
---
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