Merge branch 'knepley/fix-swarm-add-point' into 'main'

Swarm: Initial size is -1, so addition function were wrong

See merge request petsc/petsc!8541

Author: balay

src/dm/impls/swarm/data_bucket.c

@@ -538,14 +538,15 @@ PetscErrorCode DMSwarmDataBucketZeroPoint(const DMSwarmDataBucket db, const Pets
 PetscErrorCode DMSwarmDataBucketAddPoint(DMSwarmDataBucket db)
 {
   PetscFunctionBegin;
-  PetscCall(DMSwarmDataBucketSetSizes(db, db->L + 1, DMSWARM_DATA_BUCKET_BUFFER_DEFAULT));
+  PetscCall(DMSwarmDataBucketSetSizes(db, PetscMax(db->L, 0) + 1, DMSWARM_DATA_BUCKET_BUFFER_DEFAULT));
   PetscFunctionReturn(PETSC_SUCCESS);
 }
 
 /* decrement */
 PetscErrorCode DMSwarmDataBucketRemovePoint(DMSwarmDataBucket db)
 {
   PetscFunctionBegin;
+  PetscCheck(db->L > 0, PetscObjectComm((PetscObject)db), PETSC_ERR_ARG_WRONG, "Swarm has no points to be removed");
   PetscCall(DMSwarmDataBucketSetSizes(db, db->L - 1, DMSWARM_DATA_BUCKET_BUFFER_DEFAULT));
   PetscFunctionReturn(PETSC_SUCCESS);
 }

src/dm/impls/swarm/swarm.c

@@ -1772,7 +1772,7 @@ PetscErrorCode DMSwarmAddNPoints(DM dm, PetscInt npoints)
   PetscFunctionBegin;
   PetscCall(PetscLogEventBegin(DMSWARM_AddPoints, 0, 0, 0, 0));
   PetscCall(DMSwarmDataBucketGetSizes(swarm->db, &nlocal, NULL, NULL));
-  nlocal = nlocal + npoints;
+  nlocal = PetscMax(nlocal, 0) + npoints;
   PetscCall(DMSwarmDataBucketSetSizes(swarm->db, nlocal, DMSWARM_DATA_BUCKET_BUFFER_DEFAULT));
   PetscCall(PetscLogEventEnd(DMSWARM_AddPoints, 0, 0, 0, 0));
   PetscFunctionReturn(PETSC_SUCCESS);