Thank you Mark and Barry.
@Mark Adams<mailto:[email protected]> I follow you for the most part. Shouldn’t R
be an MPI Vector?
Here it goes:
Q[Vec[i]] for all "i" in my local (sequential) "Vec".
Compute number of local nonzeros in Q, call it n.
//Create a MPI Vector R, with local size n
VecCreate(PETSC_COMM_WORLD, &R);
VecSetType(R, VECMPI);
VecSetSizes(R, n, PETSC_DECIDE);
//Populate MPI Vector R with local (sequential) "Vec".
VecGetOwnershipRange(R, &istart, &iend);
local_size = iend - istart; //The local_size should be ‘n’ right?
VecGetArray(R, &values);
for (i = 0; i < local_size; i++) {
values[i] = Vec[i];
}
VecRestoreArray(R, &values);
//Scatter R to all processors
Vec V_SEQ;
VecScatter ctx;
VecScatterCreateToAll(R,&ctx,&V_SEQ);
//Remove duplicates in V_SEQ
How can I use PetscSortRemoveDupsInt to remove duplicates in V_SEQ?
Physics behind:
I am reading a parallel mesh, and want to mark all the boundary nodes. I use a
local (sequential) Vec to store the boundary nodes for each parallel partition.
Hence, local Vecs can end up with duplicate node index among them, which I
would like to get rid of when I combine all of them together.
Best,
Karthik.
From: Mark Adams <[email protected]>
Date: Friday, 9 December 2022 at 21:08
To: Chockalingam, Karthikeyan (STFC,DL,HC) <[email protected]>
Cc: Barry Smith <[email protected]>, [email protected]
<[email protected]>
Subject: Re: [petsc-users] Union of sequential vecs
If your space is pretty compact, eg, (0,12), you could create an MPI vector Q
of size 13, say, and each processor can add 1.0 to Q[Vec[i]], for all "i" in my
local "Vec".
Then each processor can count the number of local nonzeros in Q, call it n,
create a new vector, R, with local size n, then set R[i] = global index of the
nonzero for each nonzero in Q, i=0:n.
Do some sort of vec-scatter-to-all with R to get what you want.
Does that work?
Mark
On Fri, Dec 9, 2022 at 3:25 PM Karthikeyan Chockalingam - STFC UKRI via
petsc-users <[email protected]<mailto:[email protected]>> wrote:
That is where I am stuck, I don’t know who to combine them to get Vec =
{2,5,7,8,10,11,12}.
I just want them in an MPI vector.
I finally plan to call VecScatterCreateToAll so that all processor gets a copy.
Thank you.
Kind regards,
Karthik.
From: Barry Smith <[email protected]<mailto:[email protected]>>
Date: Friday, 9 December 2022 at 20:04
To: Chockalingam, Karthikeyan (STFC,DL,HC)
<[email protected]<mailto:[email protected]>>
Cc: [email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
Subject: Re: [petsc-users] Union of sequential vecs
How are you combining them to get Vec = {2,5,7,8,10,11,12}?
Do you want the values to remain on the same MPI rank as before, just in an
MPI vector?
On Dec 9, 2022, at 2:28 PM, Karthikeyan Chockalingam - STFC UKRI via
petsc-users <[email protected]<mailto:[email protected]>> wrote:
Hi,
I want to take the union of a set of sequential vectors, each living in a
different processor.
Say,
Vec_Seq1 = {2,5,7}
Vec_Seq2 = {5,8,10,11}
Vec_Seq3 = {5,2,12}.
Finally, get the union of all them Vec = {2,5,7,8,10,11,12}.
I initially wanted to create a parallel vector and insert the (sequential
vector) values but I do not know, to which index to insert the values to. But I
do know the total size of Vec (which in this case is 7).
Any help is much appreciated.
Kind regards,
Karthik.
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