BUG: sparse matrix creation in 1.13 with indices not summing entries any more #20670
Labels
defect
A clear bug or issue that prevents SciPy from being installed or used as expected
scipy.sparse
Milestone
Describe your issue.
The behaviour of sparse matrix (CSC, CSR) creation has changed in 1.13 breaking our code. Multiple data entries with the same indices are not summed up any longer but produce duplicate entries. I did not find this in the release notes. Maybe it is wanted this way, but the documentation explicitly states that conversion from COO to CSC sums up duplicate entries, so why drop this feature during creation?
Reproducing Code Example
Error message
No error message, just different sparse matrices at creation. I believe this is a bug, as the conversion, e.g. from COO format actually sums the entries as described here: https://docs.scipy.org/doc/scipy/reference/sparse.html#example-2 which is important for FEM matrices or adjacency matrices of a mesh.
SciPy/NumPy/Python version and system information
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