PETSc version 3.16.5
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# PETSC_COMM_WORLD

the equivalent of the MPI_COMM_WORLD communicator which represents all the processes that PETSc knows about.

### Notes

By default PETSC_COMM_WORLD and MPI_COMM_WORLD are identical unless you wish to run PETSc on ONLY a subset of MPI_COMM_WORLD. In that case create your new (smaller) communicator, call it, say comm, and set PETSC_COMM_WORLD = comm BEFORE calling PetscInitialize(), but after MPI_Init() has been called.

The value of PETSC_COMM_WORLD should never be USED/accessed before PetscInitialize() is called because it may not have a valid value yet.

### See Also

PETSC_COMM_SELF

### Level

beginner

### Location

include/petscsys.h

### Examples

src/sys/classes/viewer/tutorials/ex1.c.html
src/sys/classes/viewer/tutorials/ex2.c.html
src/sys/classes/viewer/tutorials/ex1f90.F90.html
src/sys/classes/random/tutorials/ex1.c.html
src/sys/classes/random/tutorials/ex2.c.html
src/sys/logging/tutorials/ex1f.F90.html
src/sys/tutorials/ex1.c.html
src/sys/tutorials/ex2.c.html
src/sys/tutorials/ex3.c.html
src/sys/tutorials/ex4.c.html
src/sys/tutorials/ex5.c.html
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Index of all manual pages