On Thu, May 24, 2012 at 2:29 PM, Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>wrote:
> Thanks for early response Jed!, > I fixed outer Krylov as PREONLY so it does not use any vectors (I guess). > Standard Vcycle includes 1 pre and 1 post smoothing. > KSP-Richardson + PC-Jacobi are ingredients for pre-smoothing and post > smoothing. > To my understanding, 2 Vectors are used by KSP Richardson + 1 Vector is > used by PC-Jacobi > at pre and post smoothing. This makes 6 vectors at each level and for 5 > levels, they should be 30! > DMSetUp_DA_nD creates and destroys two vectors as part of its set up process. There is also a scaling vector associated with restriction (so that restriction and prolongation can use the same matrix, which they usually do), including a momentary work vector used to compute the scaling. So many of those vectors are not alive at once. Are you seeing the memory used by those vectors being a significant part of the overall memory usage of the program? Barry, > > Do I think right ? > Further hint to make PCMG more memory-efficient is appreciated. > with warm regard, Abdul > > > ------------------------------ > *From:* Jed Brown <jedbrown at mcs.anl.gov> > *To:* Abdul Hanan Sheikh <hanangul12 at yahoo.co.uk>; PETSc users list < > petsc-users at mcs.anl.gov> > *Sent:* Thursday, 24 May 2012, 21:22 > *Subject:* Re: [petsc-users] Multigrid Vcycle. > > On Thu, May 24, 2012 at 2:14 PM, Abdul Hanan Sheikh < > hanangul12 at yahoo.co.uk> wrote: > > Dear all, > I am quit beginner in PETSc. > I wrote a code for multigrid Vcycle (as preconditioer) by following the > instructions on manual page. > I want to see how much memory a Vcycle allocates by default in terms of > number of matrices and vectors. > I made a try to see by comparing with jacobi preconditioner, which surely > allocates 1 vector ONLY. > It turns out that a VCycle for FIVE (5) levels including coarsest level > allocates memory for 53 vectors and > subsequently it destroys too. > > > Some of those vectors are very small due to being on the coarse level. > There are also the vectors used by the outer Krylov method. > > > > Is it normal ?? > > > Thanks in advance, > Abdul > > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120524/f7e22795/attachment.html>
