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MAHOUT-1837: Fixed dense bug in drm/package.blockify() #252

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MAHOUT-1837: Fixed dense bug in drm/package.blockify() #252

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28 changes: 12 additions & 16 deletions spark/src/main/scala/org/apache/mahout/sparkbindings/drm/package.scala
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Expand Up @@ -60,26 +60,22 @@ package object drm {
val keys = data.map(t => t._1).toArray[K]
val vectors = data.map(t => t._2).toArray

// create the block by default as dense.
// would probably be better to sample a subset of these
// vectors first before creating the entire matrix.
// so that we don't have the overhead of creating a full second matrix in
// the case that the matrix is not dense.
val block = new DenseMatrix(vectors.length, blockncol)
var row = 0
while (row < vectors.length) {
block(row, ::) := vectors(row)
row += 1
}
// create the block by default as Sparse.
val block = new SparseRowMatrix(vectors.length, blockncol, vectors, true, false)

// Test the density of the data. If the matrix does not meet the
// requirements for density, convert the Vectors to a sparse Matrix.
// Test the density of the data. If the matrix does meets the
// requirements for density, convert the Vectors to a DenseMatrix.
val resBlock = if (densityAnalysis(block)) {
block
val dBlock = new DenseMatrix(vectors.length, blockncol)
var row = 0
while (row < vectors.length) {
dBlock(row, ::) := vectors(row)
row += 1
}
dBlock
} else {
new SparseRowMatrix(vectors.length, blockncol, vectors, true, false)
block
}

Iterator(keys -> resBlock)
}
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Should the default here be a SparseRowMatrix of Random Access Sparse Vectors? Seems so. I.e.
This line should probably read:

new SparseRowMatrix(vectors.length, blockncol, vectors, true, true)

rather than:

new SparseRowMatrix(vectors.length, blockncol, vectors, true, false)

as is, correct?

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No, i believe sequential should stay as it will be more natural (ordered)
when converted to CSR which hopefuly will be our most common modus operandi
for exponential algorithms.

in fact, random access rarely makes sense at all for block-wise algorithms.

On Fri, Aug 26, 2016 at 8:03 PM, Andrew Palumbo notifications@github.com
wrote:

In spark/src/main/scala/org/apache/mahout/sparkbindings/drm/package.scala
#252 (comment):

     } else {

  •      new SparseRowMatrix(vectors.length, blockncol, vectors, true, false)

Should the default here be a SparseRowMatrix of Random Access Sparse
Vectors? Seems so. I.e.
This line should probably read:

new SparseRowMatrix(vectors.length, blockncol, vectors, true, true)

rather than:

new SparseRowMatrix(vectors.length, blockncol, vectors, true, false)

as is, correct?

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thx.

})
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