DenseMatrix.getRow() and getColumn() return deep copies of the data
-------------------------------------------------------------------
Key: MAHOUT-211
URL: https://issues.apache.org/jira/browse/MAHOUT-211
Project: Mahout
Issue Type: Bug
Components: Matrix
Affects Versions: 0.1
Environment: all
Reporter: Jake Mannix
Priority: Minor
Fix For: 0.3
As mentioned in the summary, DenseMatrix.getRow() returns a new
DenseVector(values[row]) instead of just a shallow reference. This is a)
wasteful, and b) inconsistent with what SparseRowMatrix / SparseColumnMatrix
do, which means that users who think they can mutate rows by calling getRow()
are wrong for DenseMatrix, or conversely think they can modify the row at will
are wrong for SparseRowMatrix.
Either way, we need to be consistent. I would suggest the contract be that you
get a shallow view reference (meaning, it may be an actual reference to a real
Vector, or it may be a virtual Vector, dynamically constructed, which is still
backed by entries in the matrix), so that calling Matrix.getRow(row).set(col,
value) has the same affect as Matrix.set(row, col, value). If we don't do it
this way, we should at least provide an api to get a shallow reference to rows.
Thoughts?
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
