Actual source code: borthog.c

petsc-3.3-p7 2013-05-11
```  2: /*
3:     Routines used for the orthogonalization of the Hessenberg matrix.

5:     Note that for the complex numbers version, the VecDot() and
6:     VecMDot() arguments within the code MUST remain in the order
7:     given for correct computation of inner products.
8: */
9: #include <../src/ksp/ksp/impls/gmres/gmresimpl.h>

11: /*@C
12:      KSPGMRESModifiedGramSchmidtOrthogonalization -  This is the basic orthogonalization routine
13:                 using modified Gram-Schmidt.

15:      Collective on KSP

17:   Input Parameters:
18: +   ksp - KSP object, must be associated with GMRES, FGMRES, or LGMRES Krylov method
19: -   its - one less then the current GMRES restart iteration, i.e. the size of the Krylov space

21:    Options Database Keys:
22: .  -ksp_gmres_modifiedgramschmidt - Activates KSPGMRESModifiedGramSchmidtOrthogonalization()

24:    Level: intermediate

26: .seealso:  KSPGMRESSetOrthogonalization(), KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESGetOrthogonalization()

28: @*/
31: PetscErrorCode  KSPGMRESModifiedGramSchmidtOrthogonalization(KSP ksp,PetscInt it)
32: {
33:   KSP_GMRES      *gmres = (KSP_GMRES *)(ksp->data);
35:   PetscInt       j;
36:   PetscScalar    *hh,*hes;

39:   PetscLogEventBegin(KSP_GMRESOrthogonalization,ksp,0,0,0);
40:   /* update Hessenberg matrix and do Gram-Schmidt */
41:   hh  = HH(0,it);
42:   hes = HES(0,it);
43:   for (j=0; j<=it; j++) {
44:     /* (vv(it+1), vv(j)) */
45:     VecDot(VEC_VV(it+1),VEC_VV(j),hh);
46:     *hes++ = *hh;
47:     /* vv(it+1) <- vv(it+1) - hh[it+1][j] vv(j) */
48:     VecAXPY(VEC_VV(it+1),-(*hh++),VEC_VV(j));
49:   }
50:   PetscLogEventEnd(KSP_GMRESOrthogonalization,ksp,0,0,0);
51:   return(0);
52: }

```