> No, A(t) has five diagonals as indicated by the calls to MatSetValues() with five entries per row; they correspond to the usual 5 pt stencil in 2d. This might not be the right place to ask this, but I'm new to PDE's and I expected to find something like the matrix to be used as the one derived in slides 10-12 of this presentation : https://www.math.ust.hk/~mawang/teaching/math532/mgtut.pdf
Thanks Matt for the advice on the book. I'll have a look at it.
