#include "petscdm.h" #include "petscdmlabel.h" #include "petscds.h" PetscErrorCode DMSetDefaultConstraints(DM dm, PetscSection section, Mat mat)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, l[s[i]] = c[i], where the scatter s is defined by the PetscSection returned by DMGetDefaultConstraintMatrix().
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.
collective on dm
| 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). |
Note: This increments the references of the PetscSection and the Mat, so they user can destroy them