Thanks for your explanation so much. On Tue, Jul 11, 2023 at 12:41 PM Barry Smith <bsm...@petsc.dev> wrote:
> > > On Jul 11, 2023, at 12:16 PM, neil liu <liufi...@gmail.com> wrote: > > I think I understood that. > > 1) In order to save memory, use a larger real system > > > This will save a little memory, but requires a slight change to your > model/code for your problem > > 2) vec will store the real part with imaginary part equal to zero in the > context of --scalar =complex. But this will not save memory. > > > This will waste a little memory. > > Usually, coordinates do not take much of the total memory, that is > solution vectors, matrices, intermediate work vectors for the solver take > most of the memory > so I suggest just using complex and not worrying about the few percent > memory lost. > > > > Right? > > Thanks, > > Xiaodong > > On Tue, Jul 11, 2023 at 12:03 PM neil liu <liufi...@gmail.com> wrote: > >> Do you mean that, >> >> even if I configure with --scalar=complex, when I use vecGetarray to get >> the coords, the coords array is still stored in a real manner? >> >> Thanks, >> >> Xiaodong >> >> On Tue, Jul 11, 2023 at 11:54 AM Matthew Knepley <knep...@gmail.com> >> wrote: >> >>> On Tue, Jul 11, 2023 at 11:48 AM neil liu <liufi...@gmail.com> wrote: >>> >>>> Thanks for your reply. >>>> I am using DMPLEX to read GMSH. And it seems I have to use >>>> DMGetCoordinatesLocal(); >>>> VecGetArray(veccords, &coords);//it seems coords has to be defined by >>>> complex either. >>>> >>>> 2) Store the coordinates in coords with imaginary part equal to zero. >>>> I got the coordinates from above function *VecGetArray*, therefore >>>> will this reduce the memory? >>>> >>>> 3) is a good way to work around that. >>>> >>> >>> We just store them with real part 0. >>> >>> Thanks, >>> >>> Matt >>> >>> >>>> On Tue, Jul 11, 2023 at 11:40 AM Barry Smith <bsm...@petsc.dev> wrote: >>>> >>>>> >>>>> Not really. PetscScalar (and entries of vectors etc) are either real >>>>> or complex, they cannot be mixed. >>>>> >>>>> What parts of PETSc are you using, DM? >>>>> >>>>> You can >>>>> >>>>> 1) store the coordinates in arrays and not use Vec for them. (of if >>>>> you are not using DM) >>>>> 2) sore them in Vec but with imaginary part 0 >>>>> 3) rewrite your complex systems as real systems (with twice as many >>>>> unknowns, but only real ones) >>>>> >>>>> Barry >>>>> >>>>> >>>>> > On Jul 11, 2023, at 11:34 AM, neil liu <liufi...@gmail.com> wrote: >>>>> > >>>>> > Dear Petsc developers, >>>>> > >>>>> > My computation involves both real and complex numbers. >>>>> > For example, my coordinate is real, but my matrix is complex. >>>>> > >>>>> > I use VecGetArray to get the coordinates. But it seems coordinates >>>>> have to be defined in a complex manner to be consistent with complex >>>>> matrix. >>>>> > >>>>> > Is there some ways to work around this if I understood correctly ? >>>>> > >>>>> > Thanks, >>>>> > >>>>> > Xiaodong >>>>> > >>>>> > >>>>> > >>>>> >>>>> >>> >>> -- >>> 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 >>> >>> https://www.cse.buffalo.edu/~knepley/ >>> <http://www.cse.buffalo.edu/~knepley/> >>> >> >
