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# VecTaggerSetBlockSize
block size of the set of indices returned by `VecTaggerComputeIS()`.  Values greater than one are useful when there are multiple criteria for determining which indices to include in the set.  For example, consider adaptive mesh refinement in a multiphysics problem, with metrics of solution quality for multiple fields measure on each cell.  The size of the vector will be [numCells * numFields]; the VecTagger block size should be numFields; VecTaggerComputeIS() will return indices in the range [0,numCells), i.e., one index is given for each block of values. 
## Synopsis
```
#include "petscvec.h" 
PetscErrorCode VecTaggerSetBlockSize(VecTagger tagger, PetscInt blocksize)
```
Note that the block size of the vector does not have to match.

Note also that the index set created in `VecTaggerComputeIS()` has block size: it is an index set over the list of
items that the vector refers to, not to the vector itself.

Logically Collective


## Input Parameters

- ***tagger -*** vec tagger
- ***blocksize -*** block size of the criteria used to tagger vectors





## See Also
 `VecTaggerComputeIS()`, `VecTaggerGetBlockSize()`, `VecSetBlockSize()`, `VecGetBlockSize()`, `VecTagger`, `VecTaggerCreate()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/utils/tagger/interface/tagger.c.html#VecTaggerSetBlockSize">src/vec/vec/utils/tagger/interface/tagger.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/utils/tagger/tutorials/ex1.c.html">src/vec/vec/utils/tagger/tutorials/ex1.c</A><BR>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/vec/vec/utils/tagger/interface/tagger.c)


[Index of all Vec routines](index.md)  
[Table of Contents for all manual pages](/manualpages/index.md)  
[Index of all manual pages](/manualpages/singleindex.md)  
