petsc-3.10.5 2019-03-28
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# MatNullSpaceCreate

Creates a data structure used to project vectors out of null spaces.

### Synopsis

    #include "petscmat.h"
    PetscErrorCode  MatNullSpaceCreate(MPI_Comm comm,PetscBool has_cnst,PetscInt n,const Vec vecs[],MatNullSpace *SP)

Collective on MPI_Comm

### Input Parameters

| comm | - the MPI communicator associated with the object
| has_cnst | - PETSC_TRUE if the null space contains the constant vector; otherwise PETSC_FALSE
| n | - number of vectors (excluding constant vector) in null space
| vecs | - the vectors that span the null space (excluding the constant vector); these vectors must be orthonormal. These vectors are NOT copied, so do not change them after this call. You should free the array that you pass in and destroy the vectors (this will reduce the reference count for them by one).

### Output Parameter

SP -the null space context

### Notes

See MatNullSpaceSetFunction() as an alternative way of providing the null space information instead of setting vecs.

If has_cnst is PETSC_TRUE you do not need to pass a constant vector in as a fourth argument to this routine, nor do you need to pass in a function that eliminates the constant function into MatNullSpaceSetFunction().

### Users manual sections

Section 4.19 Solving Singular Systems -

### Keywords

PC, null space, create

### See Also

MatNullSpaceDestroy(), MatNullSpaceRemove(), MatSetNullSpace(), MatNullSpace, MatNullSpaceSetFunction()

### Level

advanced

### Location

src/mat/interface/matnull.c

### Examples

src/ksp/ksp/examples/tutorials/ex29.c.html
src/ksp/ksp/examples/tutorials/ex32.c.html
src/ksp/ksp/examples/tutorials/ex34.c.html
src/ksp/ksp/examples/tutorials/ex49.c.html
src/ksp/ksp/examples/tutorials/ex50.c.html
src/ksp/ksp/examples/tutorials/ex66.c.html
src/ksp/ksp/examples/tutorials/ex67.c.html
src/ksp/ksp/examples/tutorials/ex72.c.html
src/snes/examples/tutorials/ex12.c.html
src/snes/examples/tutorials/ex62.c.html
src/snes/examples/tutorials/ex78.c.html
Index of all Mat routines
Table of Contents for all manual pages
Index of all manual pages