Going to Scipy/numpy error message

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3 years 6 months ago #3798 by ajf367
Going to Scipy/numpy error message was created by ajf367
Hello,

I have a matrix defined on a mesh as given below.
I want to make it into a larger system by placing my matrix a into a block matrix
My attempt is
Code:
a = BilinearForm(fes) a += grad(u)*grad(v)*dx length = a.mat.height Z = sp.coo_matrix((length, length)) I = sp.identity(length) B1a = sp.hstack([a.mat, Z]) B1b = sp.hstack([Z, I]) B1 = sp.vstack([B1a, B1b])
however this results in the following error message:
blocks[0,:] has incompatible row dimensions. Got blocks[0,1].shape[0] == 358240, expected 1.

How to I get around this error
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3 years 6 months ago #3832 by ddrake
Replied by ddrake on topic Going to Scipy/numpy error message
In the code snippet you posted, it looks like you may not have assembled the BilinearForm before acessing its matrix property.
Code:
a = BilinearForm(fes) a += grad(u)*grad(v)*dx a.Assemble() # <-- need to do this before accessing the matrix length = a.mat.height

Also, the NGSolve sparse matrix can't be used directly in scipy sparse like this
Code:
B1a = sp.hstack([a.mat, Z])

You might want to take a look at this: docu.ngsolve.org/latest/how_to/howto_numpy.html

Best,
Dow
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