Problem with the solver_theta function (spdiag matrix)

[apoyet]

Hi,

I'm trying to use the following file: https://github.com/hplgit/num-methods-for-PDEs/blob/master/src/diffu/diffu1D_vc.py
in order to solve the diffusion equation with non-constant diffusion coefficient.

I'm therefore using the solver_theta function. But I systematically encounters an issue when building the sparse matrix. I get the following error:

ValueError: number of diagonals (1) does not match the number of offsets (3)

Do you have any idea where this might come from ? It seems that there is an issue with the spdiags method of Scipy.

Thanks a lot in advance for your help.

Cheers,

Axel