We have an ongoing research project with Caltech where we are trying to explore ways of approximating the subspace spanned by k lowest eigen values of a given positive definite matrix(FEM discretized matrix) in a sparse format using the incomplete Cholesky factor with reduced computational complexity. So I need access to the incomplete Cholesky factor.
On Fri, Mar 30, 2018 at 6:09 PM, Wolfgang Bangerth <[email protected]> wrote: > > If I have a SparseMatrix and compute SparseILU restricting the >> sparsity to the given matrix using the functions/options given in >> https://www.dealii.org/developer/doxygen/deal.II/classSparseILU.html, >> >> >> I was wondering if there is anyway to access the Sparse matrix obtained > >> after the SparseILU decomposition. >> > > Not easily. The SparseILU class stores the information for the L and U > factors in the form of a matrix, of course, but it does not export this > matrix publicly. That's because we use the *storage format* of > SparseMatrix, but because we store two matrices in one object (namely, the > L and U factors), the thing we store this information in is not in fact a > matrix -- it's just a way to store the elements of L and U. > > What would you need this information for, if I may ask? > > > Also does dealii make use of the MKL call "dcsrilu0" to do the >> SparseILU when restricting the sparsity to the given matrix? >> > > No, SparseILU uses an implementation of our own. I suspect that this could > be improved by a great deal using interfaces to other libraries -- > contributions are always welcome! > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > www: http://www.math.colostate.edu/~bangerth/ > > -- > The deal.II project is located at http://www.dealii.org/ > For mailing list/forum options, see https://groups.google.com/d/fo > rum/dealii?hl=en > --- You received this message because you are subscribed to the Google > Groups "deal.II User Group" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
