On Mon, Sep 22, 2008 at 9:43 PM, Lisandro Dalcin <dalcinl at gmail.com> wrote: > On Mon, Sep 22, 2008 at 11:03 PM, Yujie <recrusader at gmail.com> wrote: >> Dear Lisandro: >> >> Barry has tried to establish an interface for Plapack. However, there are >> some bugs in Plapack. Therefore, it doesn't work. > > Sorry, I didn't know about those Plapack issues.
Neither did I, and seeing as how I use it, this is interesting. Please please please report any bugs you find, because I have been using it without problems. Matt >> I am wondering if CG in >> Petsc can work with parallel dense matrix. > > Of course it works. In fact, any other KSP should work. As Barry said, > The KSP methods are INDEPENDENT of the matrix format, try -pc_type > jacobi as preconditioner. > >> When using the same matrix, which >> one is faster, sequential or parallel? thanks. > > For a fixed-size matrix, you should get really good speedups iterating > in parallel. Of course, that would be even better if you can generate > the local rows of the matrix in each processor. If not, communicating > the matrix row from the 'master' to the 'slaves' could be a real > bootleneck (large data to compute at the master while slaves waiting, > large data to scatter from master to slaves), If you cannot avoid > dense matrices, then you should try hard to compute the local rows at > the owning processor. > > >> >> On Mon, Sep 22, 2008 at 6:51 PM, Lisandro Dalcin <dalcinl at gmail.com> >> wrote: >>> >>> Well, any iterative solver will actually work, but expect a really >>> poor scalability :-). I believe (never used dense matrices) that you >>> could use a direct method (PLAPACK?), but again, be prepared for long >>> running times if your problem is (even moderately) large. >>> >>> On Mon, Sep 22, 2008 at 10:35 PM, Yujie <recrusader at gmail.com> wrote: >>> > To my knowledge, PETsc doesn't provide parallel dense matrix-based >>> > solvers, >>> > such as for CG, GMRES and so on. If it is, how to deal with this >>> > problem? >>> > Thanks. >>> > >>> > Regards, >>> > >>> > Yujie >>> > >>> >>> >>> >>> -- >>> Lisandro Dalc?n >>> --------------- >>> Centro Internacional de M?todos Computacionales en Ingenier?a (CIMEC) >>> Instituto de Desarrollo Tecnol?gico para la Industria Qu?mica (INTEC) >>> Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) >>> PTLC - G?emes 3450, (3000) Santa Fe, Argentina >>> Tel/Fax: +54-(0)342-451.1594 >>> >> >> > > > > -- > Lisandro Dalc?n > --------------- > Centro Internacional de M?todos Computacionales en Ingenier?a (CIMEC) > Instituto de Desarrollo Tecnol?gico para la Industria Qu?mica (INTEC) > Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) > PTLC - G?emes 3450, (3000) Santa Fe, Argentina > Tel/Fax: +54-(0)342-451.1594 > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
