I've tried that in an earlier version. But it does not work. Then my MatMult complains that
[0]PETSC ERROR: Object is in wrong state [0]PETSC ERROR: x and y must be different vectors Because Vec[1] is then referring to Vec[0] where I am going to store the result of the MatMult. Also later on there are some AXPY that are complaining that that x and y are the same vector. Wim On Wed, Aug 30, 2017 at 2:55 PM, Stefano Zampini <[email protected]> wrote: > if you don't use KSPCreateVecs, but just a sequence of VecDuplicates, then > you can swap pointers > > Vec tmp = Z_Vec[pipe_l]; > for(int i = pipe_l; i>0; i--){ > Z_Vec[i] = Z_Vec[i-1]; > } > > if you still want to use KSPCreateVecs, you need to keep track of what was > the first vector of the sequence at the time of creation, because its > address in memory points to the malloced memory for all the Vec pointers. > > > > 2017-08-30 15:45 GMT+03:00 Wim Vanroose <[email protected]>: > >> Dear Petsc Developers, >> >> We are writing a pipelined CG with deep pipelines. For this algorithm >> I need to >> store "pipe_l +1" auxiliary variables Z_Vec. I create these >> vectors as follows: >> >> Vec *Z_VEC; >> ierr = KSPCreateVecs(ksp,pipe_l+1,&Z_VEC,0,NULL);CHKERRQ(ierr); >> >> >> Then we have a loop of iterations. However at some point I have to drop >> the last >> the auxiliary vector and shift the remaining vectors one position, and >> replace the first vector with the result of a matvec. >> >> This is in the current prototype implemented as >> >> for(int i = pipe_l; i>0; i--){ >> VecCopy( Z_VEC[i-1], Z_VEC[i] ); >> } >> >> ierr = MatMult(A, Z_VEC[1], Z_VEC[0]);CHKERRQ(ierr); >> >> It looks very inefficient to me to copy the vector, if we only want to >> shift the data. >> >> Do you have examples code where this is done more efficiently? Or is >> this already a good way to do it? >> Do you have suggestions? >> >> >> Wim >> >> >> >> > > > -- > Stefano >
