petsc-3.5.4 2015-05-23

MatBackwardSolve

Solves U x = b, given a factored matrix, A = LU. D^(1/2) U x = b, given a factored symmetric matrix, A = U^T*D*U,

Synopsis

#include "petscmat.h" 
PetscErrorCode  MatBackwardSolve(Mat mat,Vec b,Vec x)

Neighbor-wise Collective on Mat and Vec

Input Parameters

	mat	- the factored matrix
	b	- the right-hand-side vector

Output Parameter

x -the result vector

Notes

MatSolve() should be used for most applications, as it performs a forward solve followed by a backward solve.

The vectors b and x cannot be the same. I.e., one cannot call MatBackwardSolve(A,x,x).

For matrix in seqsbaij format with block size larger than 1, the diagonal blocks are not implemented as D = D^(1/2) * D^(1/2) yet. MatForwardSolve() solves U^T*D y = b, and MatBackwardSolve() solves U x = y. Thus they do not provide a symmetric preconditioner.

Most users should employ the simplified KSP interface for linear solvers instead of working directly with matrix algebra routines such as this. See, e.g., KSPCreate().

MatBackwardSolve

Synopsis

Input Parameters

Output Parameter

Notes

See Also