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From mengxr <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-3418] Sparse Matrix support (CCS) and a...
Date Thu, 18 Sep 2014 01:21:09 GMT
Github user mengxr commented on a diff in the pull request:

    https://github.com/apache/spark/pull/2294#discussion_r17704445
  
    --- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/BLAS.scala ---
    @@ -197,4 +201,368 @@ private[mllib] object BLAS extends Serializable {
             throw new IllegalArgumentException(s"scal doesn't support vector type ${x.getClass}.")
         }
       }
    +
    +  // For level-3 routines, we use the native BLAS.
    +  private def nativeBLAS: NetlibBLAS = {
    +    if (_nativeBLAS == null) {
    +      _nativeBLAS = NativeBLAS
    +    }
    +    _nativeBLAS
    +  }
    +
    +  /**
    +   * C := alpha * A * B + beta * C
    +   * @param transA specify whether to use matrix A, or the transpose of matrix A. Should
be "N" or
    +   *               "n" to use A, and "T" or "t" to use the transpose of A.
    +   * @param transB specify whether to use matrix B, or the transpose of matrix B. Should
be "N" or
    +   *               "n" to use B, and "T" or "t" to use the transpose of B.
    +   * @param alpha a scalar to scale the multiplication A * B.
    +   * @param A the matrix A that will be left multiplied to B. Size of m x k.
    +   * @param B the matrix B that will be left multiplied by A. Size of k x n.
    +   * @param beta a scalar that can be used to scale matrix C.
    +   * @param C the resulting matrix C. Size of m x n.
    +   */
    +  def gemm(
    +      transA: Boolean,
    +      transB: Boolean,
    +      alpha: Double,
    +      A: Matrix,
    +      B: DenseMatrix,
    +      beta: Double,
    +      C: DenseMatrix): Unit = {
    +    if (alpha == 0.0) {
    +      logWarning("gemm: alpha is equal to 0. Returning C.")
    --- End diff --
    
    `gemm` maybe called many times and there are cases when `alpha` is indeed zero. Maybe
we can change it to `logDebug` to avoid outputting many log messages at a normal level.


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