1 /*
2 Routines used for the orthogonalization of the Hessenberg matrix.
3
4 Note that for the complex numbers version, the VecDot() and
5 VecMDot() arguments within the code MUST remain in the order
6 given for correct computation of inner products.
7 */
8 #include <../src/ksp/ksp/impls/gmres/gmresimpl.h>
9
10 /*@C
11 KSPGMRESModifiedGramSchmidtOrthogonalization - This is the basic orthogonalization routine
12 using modified Gram-Schmidt.
13
14 Collective, No Fortran Support
15
16 Input Parameters:
17 + ksp - `KSP` object, must be associated with `KSPGMRES`, `KSPFGMRES`, or `KSPLGMRES` Krylov method
18 - it - one less than the current GMRES restart iteration, i.e. the size of the Krylov space
19
20 Options Database Key:
21 . -ksp_gmres_modifiedgramschmidt - Activates `KSPGMRESModifiedGramSchmidtOrthogonalization()`
22
23 Level: intermediate
24
25 Note:
26 In general this is much slower than `KSPGMRESClassicalGramSchmidtOrthogonalization()` but has better stability properties.
27
28 .seealso: [](ch_ksp), `KSPGMRESSetOrthogonalization()`, `KSPGMRESClassicalGramSchmidtOrthogonalization()`, `KSPGMRESGetOrthogonalization()`
29 @*/
KSPGMRESModifiedGramSchmidtOrthogonalization(KSP ksp,PetscInt it)30 PetscErrorCode KSPGMRESModifiedGramSchmidtOrthogonalization(KSP ksp, PetscInt it)
31 {
32 KSP_GMRES *gmres = (KSP_GMRES *)ksp->data;
33 PetscInt j;
34 PetscScalar *hh, *hes;
35
36 PetscFunctionBegin;
37 PetscCall(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 PetscCall(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 PetscCall(VecAXPY(VEC_VV(it + 1), -(*hh++), VEC_VV(j)));
49 }
50 PetscCall(PetscLogEventEnd(KSP_GMRESOrthogonalization, ksp, 0, 0, 0));
51 PetscFunctionReturn(PETSC_SUCCESS);
52 }
53