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Re: Zeros in matrices

 


Anders Logg wrote:
On Fri, Apr 27, 2007 at 05:24:34PM +0200, Garth N. Wells wrote:
Anders Logg wrote:
I'm comparing the entries in the Stokes systems between the new code
and the old and there seem to be quite a few more zeros in the sparse
matrix than before.

Strange. Have you counted the non-zeroes, or are you displaying the matrix?
Displaying the matrix and counting everything that looks like zero.
(Just looking at the numbers.)

There are about double the number of non-zeros (you can get the number 
by A.nnz()) for the Stokes example with the new version compared to 
version 0.6.4. For poisson and elasticity, the number of non-zeroes is 
the same as with version 0.6.4. The linear algebra looks fine - 
something is going on with the computation of the sparsity pattern for 
the Stokes problem.
Garth


/Anders


Garth

Could this have anything to do with the initialization of uBlas
matrices with a sparsity pattern and not using the temporary storage
as before? Did we have a check that removed zeros?

I haven't tried with PETSc.

/Anders
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