Esteemed colleagues,
My problem is: Div ( Grad ( phi ) ) = 0 mesh: 0 < x < 1; 0 < y < 1; with boundary conditions: phi ( x , 0 ) = x; phi ( 0 ,y ) = x; phi ( x , 1 ) = x; phi ( 1 ,y ) = x; with serial processing. solved with ( KSPCG x PCJACOBI ) and (KSPGMRS x PCJACOBI). I have a question, why the "*norm error** **of the solution*" of GMRES is high, when the mesh is large. It is a problem in methods or truncation error? the results were: *m* *n* *m x n* *error ( KSPCG x PCJACOBI )* *error ( KSPGMRS x PCJACOBI ) * 3 3 9 1,92E-16 4,42E-16 4 4 16 2,08E-16 6,46E-16 5 5 25 4,41E-16 9,63E-16 6 6 36 8,77E-16 8,26E-16 7 7 49 2,37E-06 2,52E-06 8 8 64 1,17E-05 1,33E-05 9 9 81 9,32E-06 1,26E-05 10 10 100 7,33E-06 9,93E-06 20 20 400 4,22E-05 3,16E-04 30 30 900 1,06E-04 2,37E-02 40 40 1600 2,14E-04 3,77E-02 50 50 2500 3,37E-04 9,36E-03 100 100 10000 1,27E-03 6,53E-02 200 200 40000 4,32E-03 3,67E-01 300 300 90000 9,53E-02 1,02E+00 400 400 160000 1,68E-02 2,10E+00 500 500 250000 2,61E-02 3,66E+00 how can I improve the performance of GMRES? a good week for all. -- Ph.d student Marcelo Xavier Guterres Rio de Janeiro , Brazil. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130219/8a34a223/attachment.html>
