Actual source code: agmresleja.c

      1: /*
      2:    Functions in this file reorder the Ritz values in the (modified) Leja order.
      3: */
      4: #include <../src/ksp/ksp/impls/gmres/agmres/agmresimpl.h>

      6: static PetscErrorCode KSPAGMRESLejafmaxarray(PetscScalar *re, PetscInt pt, PetscInt n, PetscInt *pos)
      7: {
      8:   PetscInt    i;
      9:   PetscScalar mx;

     11:   PetscFunctionBegin;
     12:   mx   = re[0];
     13:   *pos = 0;
     14:   for (i = pt; i < n; i++) {
     15:     if (mx < re[i]) {
     16:       mx   = re[i];
     17:       *pos = i;
     18:     }
     19:   }
     20:   PetscFunctionReturn(PETSC_SUCCESS);
     21: }

     23: static PetscErrorCode KSPAGMRESLejaCfpdMax(PetscScalar *rm, PetscScalar *im, PetscInt *spos, PetscInt nbre, PetscInt n, PetscInt *rpos)
     24: {
     25:   PetscScalar rd, id, pd, max;
     26:   PetscInt    i, j;

     28:   PetscFunctionBegin;
     29:   pd    = 1.0;
     30:   max   = 0.0;
     31:   *rpos = 0;
     32:   for (i = 0; i < n; i++) {
     33:     for (j = 0; j < nbre; j++) {
     34:       rd = rm[i] - rm[spos[j]];
     35:       id = im[i] - im[spos[j]];
     36:       pd = pd * PetscSqrtReal(rd * rd + id * id);
     37:     }
     38:     if (max < pd) {
     39:       *rpos = i;
     40:       max   = pd;
     41:     }
     42:     pd = 1.0;
     43:   }
     44:   PetscFunctionReturn(PETSC_SUCCESS);
     45: }

     47: PetscErrorCode KSPAGMRESLejaOrdering(PetscScalar *re, PetscScalar *im, PetscScalar *rre, PetscScalar *rim, PetscInt m)
     48: {
     49:   PetscInt    *spos;
     50:   PetscScalar *n_cmpl, temp;
     51:   PetscInt     i, pos, j;

     53:   PetscFunctionBegin;
     54:   PetscCall(PetscMalloc1(m, &n_cmpl));
     55:   PetscCall(PetscMalloc1(m, &spos));
     56:   /* Check the proper order of complex conjugate pairs */
     57:   j = 0;
     58:   while (j < m) {
     59:     if (im[j] != 0.0) {  /* complex eigenvalue */
     60:       if (im[j] < 0.0) { /* change the order */
     61:         temp      = im[j + 1];
     62:         im[j + 1] = im[j];
     63:         im[j]     = temp;
     64:       }
     65:       j += 2;
     66:     } else j++;
     67:   }

     69:   for (i = 0; i < m; i++) n_cmpl[i] = PetscSqrtReal(re[i] * re[i] + im[i] * im[i]);
     70:   PetscCall(KSPAGMRESLejafmaxarray(n_cmpl, 0, m, &pos));
     71:   j = 0;
     72:   if (im[pos] >= 0.0) {
     73:     rre[0] = re[pos];
     74:     rim[0] = im[pos];
     75:     j++;
     76:     spos[0] = pos;
     77:   }
     78:   while (j < (m)) {
     79:     if (im[pos] > 0) {
     80:       rre[j]  = re[pos + 1];
     81:       rim[j]  = im[pos + 1];
     82:       spos[j] = pos + 1;
     83:       j++;
     84:     }
     85:     PetscCall(KSPAGMRESLejaCfpdMax(re, im, spos, j, m, &pos));
     86:     if (im[pos] < 0) pos--;

     88:     if ((im[pos] >= 0) && (j < m)) {
     89:       rre[j]  = re[pos];
     90:       rim[j]  = im[pos];
     91:       spos[j] = pos;
     92:       j++;
     93:     }
     94:   }
     95:   PetscCall(PetscFree(spos));
     96:   PetscCall(PetscFree(n_cmpl));
     97:   PetscFunctionReturn(PETSC_SUCCESS);
     98: }