You could try using the new function A.ident_zeros() which should fix all the rows which are zero (inserting one on the diagonal).
-- Anders On Wed, Mar 10, 2010 at 06:13:39PM -0000, dbeacham wrote: > New question #103905 on DOLFIN: > https://answers.launchpad.net/dolfin/+question/103905 > > I've finally got round to calculating the dofs on a boundary from a mesh > function, so that I can go about trying to solve a pde purely on the > boundary. However, I can't quite work out how best to play about with the > assembled system: > > If I have: > > a = ( .. )*ds(i) > L = ( .. )*ds(i) > > A = assemble(a, exterior_facet_domains=meshfn) > b = assemble(L, exterior_facet_domains=meshfn) > > then, as far as I can tell I have two basic options, but I'm not sure what is > best, and can't get (2) to work: > > 1. Do something along the lines of A_sub = A.vector()[rows, cols] (where rows > = cols, is the dofs on which I wish to solve), ditto for b, and then solve > using numpy (maybe I can put it back into a GenericMatrix and use one of the > dolfin solvers, but I've certainly changed the structure and don't know how > to do it anyway). > > 2. Adjust A,b appropriately as: > A.ident(unused_dofs) > b[unused_dofs] = 0.0 > > But this method throws up an error from petsc about the object not being in > the correct state. > > Matrix of size 10201 x 10201 has 0 nonzero entries. > [0]PETSC ERROR: --------------------- Error Message > ------------------------------------ > [0]PETSC ERROR: Object is in wrong state! > [0]PETSC ERROR: Matrix is missing diagonal entry in row 10200! > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: Petsc Release Version 3.0.0, Patch 11, Mon Feb 1 11:01:51 > CST 2010 > [0]PETSC ERROR: See docs/changes/index.html for recent updates. > [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting. > [0]PETSC ERROR: See docs/index.html for manual pages. > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: Unknown Name on a linux-gnu named lappytop-dos by dbeacham > Wed Mar 10 17:49:18 2010 > [0]PETSC ERROR: Libraries linked from /home/dbeacham/FEM/stable/build/lib > [0]PETSC ERROR: Configure run at Thu Feb 11 11:37:57 2010 > [0]PETSC ERROR: Configure options COPTFLAGS=-O3 --with-debugging=0 > --with-shared=1 --with-clanguage=cxx --download-umfpack=1 > --prefix=/home/dbeacham/FEM/stable/build > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: MatZeroRows_SeqAIJ() line 1367 in src/mat/impls/aij/seq/aij.c > [0]PETSC ERROR: MatZeroRows() line 4856 in src/mat/interface/matrix.c > [0]PETSC ERROR: MatZeroRowsIS() line 4913 in src/mat/interface/matrix.c > > Thanks for any help, > David > > You received this question notification because you are a member of > DOLFIN Team, which is an answer contact for DOLFIN. > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : [email protected] > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp
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