petsc-3.7.1 2016-05-15
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# MatZeroRowsLocal

Zeros all entries (except possibly the main diagonal) of a set of rows of a matrix; using local numbering of rows.

### Synopsis

    #include "petscmat.h"
    PetscErrorCode MatZeroRowsLocal(Mat mat,PetscInt numRows,const PetscInt rows[],PetscScalar diag,Vec x,Vec b)

Collective on Mat Many br

### Input Parameters

| mat | - the matrix Many br
| numRows | - the number of rows to remove Many br
| rows | - the global row indices Many br
| diag | - value put in all diagonals of eliminated rows Many br
| x | - optional vector of solutions for zeroed rows (other entries in vector are not used) Many br
| b | - optional vector of right hand side, that will be adjusted by provided solution Many br

### Notes

Before calling MatZeroRowsLocal(), the user must first set the Many brlocal-to-global mapping by calling MatSetLocalToGlobalMapping(). Many br

For the AIJ matrix formats this removes the old nonzero structure, Many brbut does not release memory. For the dense and block diagonal Many brformats this does not alter the nonzero structure. Many br

If the option MatSetOption(mat,MAT_KEEP_NONZERO_PATTERN,PETSC_TRUE) the nonzero structure Many brof the matrix is not changed (even for AIJ and BAIJ matrices) the values are Many brmerely zeroed. Many br

The user can set a value in the diagonal entry (or for the AIJ and Many brrow formats can optionally remove the main diagonal entry from the Many brnonzero structure as well, by passing 0.0 as the final argument). Many br

You can call MatSetOption(mat,MAT_NO_OFF_PROC_ZERO_ROWS,PETSC_TRUE) if each process indicates only rows it Many browns that are to be zeroed. This saves a global synchronization in the implementation. Many br

Many br

### See Also

MatZeroRows(), MatZeroRowsLocalIS(), MatZeroEntries(), MatZeroRows(), MatSetLocalToGlobalMapping

Level:intermediate
Location:src/mat/interface/matrix.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages