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 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:    Notes:
     25:      In general this is much slower than KSPGMRESClassicalGramSchmidtOrthogonalization() but has better stability properties.

     27:    Level: intermediate

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

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

     40:   PetscLogEventBegin(KSP_GMRESOrthogonalization,ksp,0,0,0);
     41:   /* update Hessenberg matrix and do Gram-Schmidt */
     42:   hh  = HH(0,it);
     43:   hes = HES(0,it);
     44:   for (j=0; j<=it; j++) {
     45:     /* (vv(it+1), vv(j)) */
     46:     VecDot(VEC_VV(it+1),VEC_VV(j),hh);
     47:     KSPCheckDot(ksp,*hh);
     48:     if (ksp->reason) break;
     49:     *hes++ = *hh;
     50:     /* vv(it+1) <- vv(it+1) - hh[it+1][j] vv(j) */
     51:     VecAXPY(VEC_VV(it+1),-(*hh++),VEC_VV(j));
     52:   }
     53:   PetscLogEventEnd(KSP_GMRESOrthogonalization,ksp,0,0,0);
     54:   return(0);
     55: }