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# VecSetValues

Inserts or adds values into certain locations of a vector.

## Synopsis

    #include "petscvec.h"
    PetscErrorCode VecSetValues(Vec x, PetscInt ni, const PetscInt ix[], const PetscScalar y[], InsertMode iora)

Not Collective

## Input Parameters

- x - vector to insert in

- ni - number of elements to add

- ix - indices where to add

- y - array of values. Pass `NULL` to set all zeroes.

- iora - either `INSERT_VALUES` to replace the current values or `ADD_VALUES` to add values to any existing entries

## Notes

       `VecSetValues()` sets x[ix[i]] = y[i], for i=0,...,ni-1.

Calls to `VecSetValues()` with the `INSERT_VALUES` and `ADD_VALUES` options cannot be mixed without intervening calls to the assembly routines.

These values may be cached, so `VecAssemblyBegin()` and `VecAssemblyEnd()` MUST be called after all calls to `VecSetValues()` have been completed.

VecSetValues() uses 0-based indices in Fortran as well as in C.

If you call `VecSetOption`(x, `VEC_IGNORE_NEGATIVE_INDICES`,`PETSC_TRUE`), negative indices may be passed in ix. These rows are simply ignored. This allows easily inserting element load matrices with homogeneous Dirichlet boundary conditions that you don’t want represented in the vector.

## Fortran Note

If any of `ix` and `y` are scalars pass them using, for example,

      call VecSetValues(mat, one, [ix], [y], INSERT_VALUES, ierr)

## See Also

Vectors and Parallel Data, `Vec`, `VecAssemblyBegin()`, `VecAssemblyEnd()`, `VecSetValuesLocal()`, `VecSetValue()`, `VecSetValuesBlocked()`, `InsertMode`, `INSERT_VALUES`, `ADD_VALUES`, `VecGetValues()`

## Level

beginner

## Location

src/vec/vec/interface/rvector.c

## Examples

src/ksp/ksp/tutorials/ex54.c
src/ksp/ksp/tutorials/ex35.cxx
src/ksp/ksp/tutorials/ex43.c
src/ksp/ksp/tutorials/ex51.c
src/ksp/ksp/tutorials/ex25.c
src/ksp/ksp/tutorials/ex36.cxx
src/ksp/ksp/tutorials/ex28.c
src/ksp/ksp/tutorials/ex3.c

## Implementations

VecSetValues_MPI() in src/vec/vec/impls/mpi/pdvec.c
VecSetValues_Seq() in src/vec/vec/impls/seq/bvec2.c

Index of all Vec routines
Table of Contents for all manual pages
Index of all manual pages