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[Dominique <question121973@xxxxxxxxxxxxxxxxxxxxx>]

New question #121973 on DOLFIN:
https://answers.launchpad.net/dolfin/+question/121973

Hello,

The questions below are PETSc-related so please let me know if I really should ask them elsewhere.

I'm generating a sparse coefficient matrix A using

A = assemble(a)

where a is some bilinear form. I'm wondering how I can access the arrays that describe A in compressed sparse row format. I thought A.data would do the job but:

In [61]: A.data?
Type:		instancemethod
Base Class:	<type 'instancemethod'>
String Form:	<bound method Matrix.data of <dolfin.cpp.Matrix; proxy of <Swig Object of type 'dolfin::Matrix *' at 0x916ab18> >>
Namespace:	Interactive
File:		/home/orban/Work/FEniCS/lib/python2.6/site-packages/dolfin/cpp.py
Definition:	A.data(self)
Docstring:
    Return arrays to underlying compresssed row/column storage data 


In [62]: A.data()
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)

/home/orban/Envs/sparse/dev/fenics/<ipython console> in <module>()

/home/orban/Work/FEniCS/lib/python2.6/site-packages/dolfin/cpp.pyc in data(self)
   2124         """ Return arrays to underlying compresssed row/column storage data """
   2125 
-> 2126         return self._data()
   2127 
   2128     def __getitem__(self,indices):

RuntimeError: *** Error: Unable to return pointers to underlying matrix data.


I'm using FEniCS under Fedora.

Also, I can compute matrix-vector products with A*x, but is there a better way to compute transpose matrix-vector products than with A.transpmult?

Thanks!
Dominique

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