Actual source code: borthog.c
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
17: Input Parameters:
18: + ksp - KSP object, must be associated with `KSPGMRES`, `KSPFGMRES`, or `KSPLGMRES` 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: Notes:
27: In general this is much slower than `KSPGMRESClassicalGramSchmidtOrthogonalization()` but has better stability properties.
29: .seealso: [](chapter_ksp), `KSPGMRESSetOrthogonalization()`, `KSPGMRESClassicalGramSchmidtOrthogonalization()`, `KSPGMRESGetOrthogonalization()`
30: @*/
31: PetscErrorCode KSPGMRESModifiedGramSchmidtOrthogonalization(KSP ksp, PetscInt it)
32: {
33: KSP_GMRES *gmres = (KSP_GMRES *)(ksp->data);
34: PetscInt j;
35: PetscScalar *hh, *hes;
37: PetscLogEventBegin(KSP_GMRESOrthogonalization, ksp, 0, 0, 0);
38: /* update Hessenberg matrix and do Gram-Schmidt */
39: hh = HH(0, it);
40: hes = HES(0, it);
41: for (j = 0; j <= it; j++) {
42: /* (vv(it+1), vv(j)) */
43: VecDot(VEC_VV(it + 1), VEC_VV(j), hh);
44: KSPCheckDot(ksp, *hh);
45: if (ksp->reason) break;
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: }