DMSetDefaultConstraints#

Set the PetscSection and Mat that specify the local constraint interpolation.

Synopsis#

#include "petscdm.h"          
#include "petscdmlabel.h"     
#include "petscds.h"     
PetscErrorCode DMSetDefaultConstraints(DM dm, PetscSection section, Mat mat, Vec bias)

If a constraint matrix is specified, then it is applied during DMGlobalToLocalEnd() when mode is INSERT_VALUES, INSERT_BC_VALUES, or INSERT_ALL_VALUES. Without a constraint matrix, the local vector l returned by DMGlobalToLocalEnd() contains values that have been scattered from a global vector without modification; with a constraint matrix A, l is modified by computing c = A * l + bias, l[s[i]] = c[i], where the scatter s is defined by the PetscSection returned by DMGetDefaultConstraints().

If a constraint matrix is specified, then its adjoint is applied during DMLocalToGlobalBegin() when mode is ADD_VALUES, ADD_BC_VALUES, or ADD_ALL_VALUES. Without a constraint matrix, the local vector l is accumulated into a global vector without modification; with a constraint matrix A, l is first modified by computing c[i] = l[s[i]], l[s[i]] = 0, l = l + A’*c, which is the adjoint of the operation described above. Any bias, if specified, is ignored when accumulating.

collective on dm

Input Parameters#

  • dm - The DM

  • section - The PetscSection describing the range of the constraint matrix: relates rows of the constraint matrix to dofs of the default section. Must have a local communicator (PETSC_COMM_SELF or derivative).

  • mat - The Mat that interpolates local constraints: its width should be the layout size of the default section: NULL indicates no constraints. Must have a local communicator (PETSC_COMM_SELF or derivative).

  • bias - A bias vector to be added to constrained values in the local vector. NULL indicates no bias. Must have a local communicator (PETSC_COMM_SELF or derivative).

Note#

This increments the references of the PetscSection, Mat, and Vec, so they user can destroy them.

See Also#

DMGetDefaultConstraints()

Level#

advanced

Location#

src/dm/interface/dm.c


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