Try this to see if it helps:
diff --git a/src/sys/utils/sorti.c b/src/sys/utils/sorti.c
index 1b07205a..90779891 100644
--- a/src/sys/utils/sorti.c
+++ b/src/sys/utils/sorti.c
@@ -294,7 +294,8 @@ static PetscErrorCode
PetscSortIntWithArrayPair_Private(PetscInt *L,PetscInt *J,
}
PetscFunctionReturn(0);
}
- SWAP3(L[0],L[right/2],J[0],J[right/2],K[0],K[right/2],tmp);
+ i = MEDIAN(L,right);
+ SWAP3(L[0],L[i],J[0],J[i],K[0],K[i],tmp);
vl = L[0];
last = 0;
for (i=1; i<=right; i++) {
On Tue, Jul 2, 2019 at 12:14 PM Fande Kong via petsc-dev
<[email protected]<mailto:[email protected]>> wrote:
BTW,
PetscSortIntWithArrayPair is used in MatStashSortCompress_Private.
Any way to avoid to use PetscSortIntWithArrayPair in
MatStashSortCompress_Private?
Fande,
On Tue, Jul 2, 2019 at 11:09 AM Fande Kong
<[email protected]<mailto:[email protected]>> wrote:
Hi Developers,
John just noticed that the matrix assembly was slow when having sufficient
amount of off-diagonal entries. It was not a MPI issue since I was able to
reproduce the issue using two cores on my desktop, that is, "mpirun -n 2".
I turned on a profiling, and 99.99% of the time was spent on
PetscSortIntWithArrayPair (recursively calling). It took THREE MINUTES to
get the assembly done. And then changed to use the option "-matstash_legacy" to
restore
the code to the old assembly routine, and the same code took ONE SECOND to get
the matrix assembly done.
Should write any better sorting algorithms?
Fande,
