On Thu, Aug 9, 2012 at 11:22 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Thu, Aug 9, 2012 at 10:19 PM, Yifei Li <yifli82 at gmail.com> wrote: > >> >> >> On Thu, Aug 9, 2012 at 10:59 PM, Matthew Knepley <knepley at gmail.com>wrote: >> >>> On Thu, Aug 9, 2012 at 9:56 PM, Yifei Li <yifli82 at gmail.com> wrote: >>> >>>> Matt, >>>> >>>> I'm new to PETSC, can you pls explain what you mean by 'keep it in >>>> unassembled form'? >>>> >>> >>> Just keep two vectors, u^T v, instead of the dense matrix. >>> >>> >> But I need the result of the outer product (e.g, A) for >> further calculation (e.g., A*W). >> > > A * W = A * (u v^T) = (A * u) v^T > > Ah, how come I missed such a simple technique thanks :) > > > Matt > > >> >>> >>> Matt >>> >>> >>>> A small example would be nice too. Thanks >>>> >>>> Yifei >>>> >>>> On Thu, Aug 9, 2012 at 9:15 PM, Matthew Knepley <knepley at >>>> gmail.com>wrote: >>>> >>>>> On Thu, Aug 9, 2012 at 5:39 PM, Yifei Li <yifli82 at gmail.com> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> I did not find any function doing this in the manual. Could someone >>>>>> suggest a good way to do this? >>>>>> >>>>> >>>>> That gives a dense matrix. You would never want to do this. You would >>>>> keep it in unassembled form. >>>>> >>>>> Matt >>>>> >>>>> >>>>>> >>>>>> Thanks >>>>>> >>>>>> Yifei >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> 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 >>>>> >>>> >>>> >>> >>> >>> -- >>> 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 >>> >> >> > > > -- > 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 > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120809/353f7bf4/attachment.html>
