On Thu, Jul 16, 2015 at 1:31 PM, Barry Smith <[email protected]> wrote:
> > > On Jul 16, 2015, at 11:14 AM, Jed Brown <[email protected]> wrote: > > > > Gianluca Meneghello <[email protected]> writes: > > > >> Hi again, > >> > >> I am now trying to write a vector to an HDF5, this time using a DM > >> structure to impose the vector layout. > >> > >> Creating the vector with (as in src/dm/examples/tutorials/ex10.c) > >> > >> DMCreateGlobalVector(da2D,&gauss); > >> > >> every works fine, i.e. the hdf5 file has the correct layout given by the > >> dimension of the DM. On the other side, if I use: > >> > >> VecCreate(PETSC_COMM_WORLD,&gauss); > >> VecSetSizes(gauss,PETSC_DECIDE,Nx*Ny); > >> VecSetDM(gauss,da2D); > > > > VecSetDM only associates a DM with the Vec. It does not interpose > > itself into VecView. > > > > Should we change this so that creating a Vec of the correct size/block > > size/layout and associating a DM is equivalent? Perhaps, but it's more > > nuanced than it might seem. > > Yikes. VecSetDM() seems a very dangerous and odd thing. Should it exist? > If it exists it seems it should be exactly equivalent to creating the > vector from the DM. > I tend to disagree. It is used to set a member variable which is not exposed: find src -name "*.c" | xargs grep VecSetDM src/dm/impls/composite/pack.c: ierr = VecSetDM(*gvec, dm);CHKERRQ(ierr); src/dm/impls/composite/pack.c: ierr = VecSetDM(*lvec, dm);CHKERRQ(ierr); src/dm/impls/da/dadist.c: ierr = VecSetDM(*g, da);CHKERRQ(ierr); src/dm/impls/da/dalocal.c: ierr = VecSetDM(*g, da);CHKERRQ(ierr); src/dm/impls/network/networkcreate.c: ierr = VecSetDM(*vec,dm);CHKERRQ(ierr); src/dm/impls/network/networkcreate.c: ierr = VecSetDM(*vec,dm);CHKERRQ(ierr); src/dm/impls/redundant/dmredundant.c: ierr = VecSetDM(*gvec,dm);CHKERRQ(ierr); src/dm/impls/redundant/dmredundant.c: ierr = VecSetDM(*lvec,dm);CHKERRQ(ierr); src/dm/impls/shell/dmshell.c: ierr = VecSetDM(*gvec,dm);CHKERRQ(ierr); src/dm/impls/shell/dmshell.c: ierr = VecSetDM(*gvec,dm);CHKERRQ(ierr); src/dm/impls/sliced/sliced.c: ierr = VecSetDM(*gvec,dm);CHKERRQ(ierr); src/dm/interface/dmi.c: ierr = VecSetDM(*vec, dm);CHKERRQ(ierr); src/dm/interface/dmi.c: ierr = VecSetDM(*vec, dm);CHKERRQ(ierr); src/dm/interface/ftn-auto/dmf.c:*__ierr = VecSetDM( I don't like putting in a bunch of side-effects. Those come from actually being created from a DM, which is correct. Matt > > > > Why don't you want to just call DMCreateGlobalVector()? > > -- 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
