PETSC_EXTERN void PETSC_STDCALL veccreateghostwitharray_(MPI_Comm *comm,PetscInt *n,PetscInt *N,PetscInt *nghost,PetscInt *ghosts,PetscScalar *array,
Vec *vv,PetscErrorCode *ierr)
{
CHKFORTRANNULLSCALAR(array);
*ierr = VecCreateGhostWithArray(MPI_Comm_f2c(*(MPI_Fint*)&*comm),*n,*N,*nghost,
ghosts,array,vv);
}
/*@
VecCreateGhost - Creates a parallel vector with ghost padding on each processor.
Collective on MPI_Comm
Input Parameters:
+ comm - the MPI communicator to use
. n - local vector length
. N - global vector length (or PETSC_DECIDE to have calculated if n is given)
. nghost - number of local ghost points
- ghosts - global indices of ghost points, these do not need to be in increasing order (sorted)
Output Parameter:
. vv - the global vector representation (without ghost points as part of vector)
Notes:
Use VecGhostGetLocalForm() to access the local, ghosted representation
of the vector.
This also automatically sets the ISLocalToGlobalMapping() for this vector.
Level: advanced
Concepts: vectors^ghosted
.seealso: VecCreateSeq(), VecCreate(), VecDuplicate(), VecDuplicateVecs(), VecCreateMPI(),
VecGhostGetLocalForm(), VecGhostRestoreLocalForm(), VecGhostUpdateBegin(),
VecCreateGhostWithArray(), VecCreateMPIWithArray(), VecGhostUpdateEnd(),
VecCreateGhostBlock(), VecCreateGhostBlockWithArray(), VecMPISetGhost()
@*/
PetscErrorCode VecCreateGhost(MPI_Comm comm,PetscInt n,PetscInt N,PetscInt nghost,const PetscInt ghosts[],Vec *vv)
{
PetscErrorCode ierr;
PetscFunctionBegin;
ierr = VecCreateGhostWithArray(comm,n,N,nghost,ghosts,0,vv);CHKERRQ(ierr);
PetscFunctionReturn(0);
}
int main(int argc,char **argv)
{
PetscMPIInt rank,size;
PetscInt nlocal = 6,nghost = 2,ifrom[2],i,rstart,rend;
PetscErrorCode ierr;
PetscBool flg,flg2;
PetscScalar value,*array,*tarray=0;
Vec lx,gx,gxs;
PetscInitialize(&argc,&argv,(char *)0,help);
ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRQ(ierr);
ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRQ(ierr);
if (size != 2) SETERRQ(PETSC_COMM_SELF,1,"Must run example with two processors\n");
/*
Construct a two dimensional graph connecting nlocal degrees of
freedom per processor. From this we will generate the global
indices of needed ghost values
For simplicity we generate the entire graph on each processor:
in real application the graph would stored in parallel, but this
example is only to demonstrate the management of ghost padding
with VecCreateGhost().
In this example we consider the vector as representing
degrees of freedom in a one dimensional grid with periodic
boundary conditions.
----Processor 1--------- ----Processor 2 --------
0 1 2 3 4 5 6 7 8 9 10 11
|----|
|-------------------------------------------------|
*/
if (!rank) {
ifrom[0] = 11; ifrom[1] = 6;
} else {
ifrom[0] = 0; ifrom[1] = 5;
}
/*
Create the vector with two slots for ghost points. Note that both
the local vector (lx) and the global vector (gx) share the same
array for storing vector values.
*/
ierr = PetscOptionsHasName(PETSC_NULL,"-allocate",&flg);CHKERRQ(ierr);
ierr = PetscOptionsHasName(PETSC_NULL,"-vecmpisetghost",&flg2);CHKERRQ(ierr);
if (flg) {
ierr = PetscMalloc((nlocal+nghost)*sizeof(PetscScalar),&tarray);CHKERRQ(ierr);
ierr = VecCreateGhostWithArray(PETSC_COMM_WORLD,nlocal,PETSC_DECIDE,nghost,ifrom,tarray,&gxs);CHKERRQ(ierr);
} else if (flg2) {
ierr = VecCreate(PETSC_COMM_WORLD,&gxs);CHKERRQ(ierr);
ierr = VecSetType(gxs,VECMPI);CHKERRQ(ierr);
ierr = VecSetSizes(gxs,nlocal,PETSC_DECIDE);CHKERRQ(ierr);
ierr = VecMPISetGhost(gxs,nghost,ifrom);CHKERRQ(ierr);
} else {
ierr = VecCreateGhost(PETSC_COMM_WORLD,nlocal,PETSC_DECIDE,nghost,ifrom,&gxs);CHKERRQ(ierr);
}
/*
Test VecDuplicate()
*/
ierr = VecDuplicate(gxs,&gx);CHKERRQ(ierr);
ierr = VecDestroy(&gxs);CHKERRQ(ierr);
/*
Access the local representation
*/
ierr = VecGhostGetLocalForm(gx,&lx);CHKERRQ(ierr);
/*
Set the values from 0 to 12 into the "global" vector
*/
ierr = VecGetOwnershipRange(gx,&rstart,&rend);CHKERRQ(ierr);
for (i=rstart; i<rend; i++) {
value = (PetscScalar) i;
ierr = VecSetValues(gx,1,&i,&value,INSERT_VALUES);CHKERRQ(ierr);
}
ierr = VecAssemblyBegin(gx);CHKERRQ(ierr);
ierr = VecAssemblyEnd(gx);CHKERRQ(ierr);
ierr = VecGhostUpdateBegin(gx,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
ierr = VecGhostUpdateEnd(gx,INSERT_VALUES,SCATTER_FORWARD);CHKERRQ(ierr);
/*
Print out each vector, including the ghost padding region.
*/
ierr = VecGetArray(lx,&array);CHKERRQ(ierr);
for (i=0; i<nlocal+nghost; i++) {
ierr = PetscSynchronizedPrintf(PETSC_COMM_WORLD,"%D %G\n",i,PetscRealPart(array[i]));CHKERRQ(ierr);
}
ierr = VecRestoreArray(lx,&array);CHKERRQ(ierr);
ierr = PetscSynchronizedFlush(PETSC_COMM_WORLD);CHKERRQ(ierr);
ierr = VecGhostRestoreLocalForm(gx,&lx);CHKERRQ(ierr);
ierr = VecDestroy(&gx);CHKERRQ(ierr);
if (flg) {ierr = PetscFree(tarray);CHKERRQ(ierr);}
ierr = PetscFinalize();
return 0;
}
