PetscSFReduceBegin

begin reduction of leafdata into rootdata, to be completed with call to PetscSFReduceEnd()

Synopsis

#include "petscsf.h" 
PetscErrorCode PetscSFReduceBegin(PetscSF sf,MPI_Datatype unit,const void *leafdata,void *rootdata,MPI_Op op)

Collective

Input Arguments

	sf	- star forest
	unit	- data type
	leafdata	- values to reduce
	op	- reduction operation

Output Arguments

rootdata

- result of reduction of values from all leaves of each root

Notes

When petsc is configured with device support, it will use its own mechanism to figure out whether the given data pointers are host pointers or device pointers, which may incur a noticable cost. If you already knew the info, you should use PetscSFReduceWithMemTypeBegin() instead.

Level

intermediate

Location

src/vec/is/sf/interface/sf.c

Examples

src/vec/is/sf/tutorials/ex1.c.html

Implementations