PETSc version 3.16.5
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# VecISCopy

Copies between a reduced vector and the appropriate elements of a full-space vector.

### Synopsis

    #include "petscvec.h"
    PetscErrorCode VecISCopy(Vec vfull, IS is, ScatterMode mode, Vec vreduced)

### Input Parameters

| vfull | - the full-space vector
| is | - the index set for the reduced space
| mode | - the direction of copying, SCATTER_FORWARD or SCATTER_REVERSE
| vreduced | - the reduced-space vector

### Output Parameters

| vfull | - the sum of the full-space vector and reduced-space vector

### Notes

The index set identifies entries in the global vector. Negative indices are skipped; indices outside the ownership range of vfull will raise an error.

mode == SCATTER_FORWARD: vfull[is[i]] = vreduced[i] mode == SCATTER_REVERSE: vreduced[i] = vfull[is[i]]

### See Also

VecAXPY(), VecGetOwnershipRange()

### Level

advanced

### Location

src/vec/vec/utils/projection.c
Index of all Vec routines
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