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https://issues.apache.org/jira/browse/MAHOUT-1960?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Trevor Grant resolved MAHOUT-1960.
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Resolution: Fixed
> Flipped sign in the SparseSparseDrmTimer.mscala causes Desnse Matrix
> multiplication
> -----------------------------------------------------------------------------------
>
> Key: MAHOUT-1960
> URL: https://issues.apache.org/jira/browse/MAHOUT-1960
> Project: Mahout
> Issue Type: Bug
> Affects Versions: 0.13.0
> Reporter: Andrew Palumbo
> Assignee: Andrew Palumbo
> Priority: Blocker
> Fix For: 0.13.0
>
>
> In {{SparseSparseDrmTimer.mscala}} with the signature:
> def timeSparseDRMMMul(m: Int, n: Int, s: Int, para: Int, pctDense: Double =
> .20, seed: Long = 1234L): Long = {
> the {{pctDense}} argument indicates the percent of nonZero elements in the
> matrix.
> As is the code to produce a random DRM for testing is as follows:
> {code}
> val drmA = drmParallelizeEmpty(m , s, para).mapBlock(){
> case (keys,block:Matrix) =>
> val R = scala.util.Random
> R.setSeed(seed)
> val blockB = new SparseRowMatrix(block.nrow, block.ncol)
> blockB := {x => if (R.nextDouble > pctDense) R.nextDouble else x }
> (keys -> blockB)
> }
> {code}
> The greater than sign in line:
> blockB := {x => if (R.nextDouble > pctDense) R.nextDouble else x }
> should be a less than sign; i.e.:
> blockB := {x => if (R.nextDouble < pctDense) R.nextDouble else x }
> This incorrect sign produces matrices of Incorrect density and can cause OOM
> errors.
>
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