Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/17940#discussion_r117480337
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala
---
@@ -992,7 +992,24 @@ object Matrices {
new DenseMatrix(dm.rows, dm.cols, dm.data, dm.isTranspose)
case sm: BSM[Double] =>
// There is no isTranspose flag for sparse matrices in Breeze
- new SparseMatrix(sm.rows, sm.cols, sm.colPtrs, sm.rowIndices,
sm.data)
+
+ // Some Breeze CSCMatrices may have extra trailing zeros in
+ // .rowIndices and .data, which are added after some matrix
+ // operations for efficiency.
+ //
+ // Therefore the last element of sm.colPtrs would no longer be
+ // coherent with the size of sm.rowIndices and sm.data
+ // despite sm being a valid CSCMatrix.
+ // We need to truncate both arrays (rowIndices, data)
+ // to the real size of the vector sm.activeSize to allow valid
conversion
+
+ if (sm.rowIndices.length > sm.activeSize) {
+ val smC = sm.copy
+ smC.compact()
+ new SparseMatrix(smC.rows, smC.cols, smC.colPtrs,
smC.rowIndices, smC.data)
+ } else {
+ new SparseMatrix(sm.rows, sm.cols, sm.colPtrs, sm.rowIndices,
sm.data)
--- End diff --
@hhbyyh what do you think of the current state? I wasn't clear if you were
requesting a specific change to the comment.
Here, if you're going to change it again, you could simplify by not
repeating the `new SparseMatrix(...)` call. Just pick which sparse matrix
you're copying in the if statement (original or compacted) and then return the
result of converting that.
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