From GraphBLAS/LAGraph#28, C-API can use GrB_assign (A, A, NULL, A, GrB_ALL, nrows, GrB_ALL, ncols, Replace) ; to drop zeros for A. But A[:A.nrows, :A.ncols] = A[:A.nrows, :A.ncols] does not work.

I need to count non-zero items columnwise. But gb.binary.gt(mxIn , 0) is BOOL and cannot do sum, gb.unary.one(mxIn).new() just set every element to one including zeros and false(s).