petsc-3.6.1 2015-08-06
MatAssemblyBegin
Begins assembling the matrix. This routine should be called after completing all calls to MatSetValues().
Synopsis
#include "petscmat.h"
PetscErrorCode MatAssemblyBegin(Mat mat,MatAssemblyType type)
Collective on Mat
Input Parameters
| mat | - the matrix
|
| type | - type of assembly, either MAT_FLUSH_ASSEMBLY or MAT_FINAL_ASSEMBLY
|
Notes
MatSetValues() generally caches the values. The matrix is ready to
use only after MatAssemblyBegin() and MatAssemblyEnd() have been called.
Use MAT_FLUSH_ASSEMBLY when switching between ADD_VALUES and INSERT_VALUES
in MatSetValues(); use MAT_FINAL_ASSEMBLY for the final assembly before
using the matrix.
ALL processes that share a matrix MUST call MatAssemblyBegin() and MatAssemblyEnd() the SAME NUMBER of times, and each time with the
same flag of MAT_FLUSH_ASSEMBLY or MAT_FINAL_ASSEMBLY for all processes. Thus you CANNOT locally change from ADD_VALUES to INSERT_VALUES, that is
a global collective operation requring all processes that share the matrix.
Space for preallocated nonzeros that is not filled by a call to MatSetValues() or a related routine are compressed
out by assembly. If you intend to use that extra space on a subsequent assembly, be sure to insert explicit zeros
before MAT_FINAL_ASSEMBLY so the space is not compressed out.
See Also
MatAssemblyEnd(), MatSetValues(), MatAssembled()
Level:beginner
Location:src/mat/interface/matrix.c
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages
Examples
src/mat/examples/tutorials/ex2.c.html
src/mat/examples/tutorials/ex5.c.html
src/mat/examples/tutorials/ex8.c.html
src/mat/examples/tutorials/ex12.c.html
src/mat/examples/tutorials/ex15.c.html
src/mat/examples/tutorials/ex16.c.html
src/mat/examples/tutorials/ex17.c.html
src/ksp/pc/examples/tutorials/ex1.c.html
src/ksp/pc/examples/tutorials/ex2.c.html
src/ksp/ksp/examples/tutorials/ex1.c.html
src/ksp/ksp/examples/tutorials/ex2.c.html