Fix a hang in write_matrix_market_csc #76
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…tter::chunk::next_chunk. Trying to calculate the chunk size with nnz_per_columns being 0, which may happen for sparse arrays with no explicit values, results in an undefined behavior (division by 0).
…dependent of the number of explicit values.
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Calling
write_matrix_market_cscon a sparse array with no explicit values hangs indefinitely. This is caused by the fact that insidecsc_formatter::chunk::next_chunk, there is a division bynnz_per_column, which happens to be0.for such arrays.The fix I propose here is to set
ptr_chunk_endto the end of range in the problematic case, avoiding division by zero.An alternative fix could be to call
write_bodyinsidewrite_matrix_market_csconly ifnnz > 0, but it doesn't really solve the problem within thecsc_formatter.I also updated unit tests to cover the case of a csc matrix with no explicit values and non-zero dimensions.