VecGhostGetLocalForm#
Obtains the local ghosted representation of a parallel vector (obtained with VecCreateGhost()
, VecCreateGhostWithArray()
or VecCreateSeq()
).
Synopsis#
#include "petscvec.h"
PetscErrorCode VecGhostGetLocalForm(Vec g, Vec *l)
Logically Collective
Input Parameter#
g - the global vector
Output Parameter#
l - the local (ghosted) representation,
NULL
ifg
is not ghosted
Notes#
This routine does not actually update the ghost values, but rather it returns a sequential vector that includes the locations for the ghost values and their current values. The returned vector and the original vector passed in share the same array that contains the actual vector data.
To update the ghost values from the locations on the other processes one must call
VecGhostUpdateBegin()
and VecGhostUpdateEnd()
before accessing the ghost values. Thus normal
usage is
VecGhostUpdateBegin(x,INSERT_VALUES,SCATTER_FORWARD);
VecGhostUpdateEnd(x,INSERT_VALUES,SCATTER_FORWARD);
VecGhostGetLocalForm(x,&xlocal);
VecGetArray(xlocal,&xvalues);
// access the non-ghost values in locations xvalues[0:n-1] and ghost values in locations xvalues[n:n+nghost];
VecRestoreArray(xlocal,&xvalues);
VecGhostRestoreLocalForm(x,&xlocal);
One should call VecGhostRestoreLocalForm()
or VecDestroy()
once one is
finished using the object.
See Also#
Vectors and Parallel Data, Vec
, VecType
, VecCreateGhost()
, VecGhostRestoreLocalForm()
, VecCreateGhostWithArray()
Level#
advanced
Location#
Examples#
src/vec/vec/tutorials/ex9.c
src/vec/vec/tutorials/ex14f.F90
src/vec/vec/tutorials/ex9f.F90
Index of all Vec routines
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Index of all manual pages