Date: 2016-07-24T16:54:48+00:00

Actual source code: dgedi.c
petsc-3.7.3 2016-07-24
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      2: /*
      3:               This file creating by running f2c
      4:             linpack. this version dated 08/14/78
      5:       cleve moler, university of new mexico, argonne national lab.

      7:       Computes the inverse of a matrix given its factors and pivots
      8:     calculated by PetscLINPACKgefa(). Performed in-place for an n by n
      9:     dense matrix.

     11:        Used by the sparse factorization routines in
     12:      src/mat/impls/baij/seq

     14: */

     16: #include <petscsys.h>

     20: PETSC_INTERN PetscErrorCode PetscLINPACKgedi(MatScalar *a,PetscInt n,PetscInt *ipvt,MatScalar *work)
     21: {
     22:   PetscInt  i__2,kb,kp1,nm1,i,j,k,l,ll,kn,knp1,jn1;
     23:   MatScalar *aa,*ax,*ay,tmp;
     24:   MatScalar t;

     27:   --work;
     28:   --ipvt;
     29:   a -= n + 1;

     31:   /*     compute inverse(u) */

     33:   for (k = 1; k <= n; ++k) {
     34:     kn      = k*n;
     35:     knp1    = kn + k;
     36:     a[knp1] = 1.0 / a[knp1];
     37:     t       = -a[knp1];
     38:     i__2    = k - 1;
     39:     aa      = &a[1 + kn];
     40:     for (ll=0; ll<i__2; ll++) aa[ll] *= t;
     41:     kp1 = k + 1;
     42:     if (n < kp1) continue;
     43:     ax = aa;
     44:     for (j = kp1; j <= n; ++j) {
     45:       jn1        = j*n;
     46:       t          = a[k + jn1];
     47:       a[k + jn1] = 0.;
     48:       ay         = &a[1 + jn1];
     49:       for (ll=0; ll<k; ll++) ay[ll] += t*ax[ll];
     50:     }
     51:   }

     53:   /*    form inverse(u)*inverse(l) */

     55:   nm1 = n - 1;
     56:   if (nm1 < 1) {
     57:       return(0);
     58:   }
     59:   for (kb = 1; kb <= nm1; ++kb) {
     60:     k   = n - kb;
     61:     kn  = k*n;
     62:     kp1 = k + 1;
     63:     aa  = a + kn;
     64:     for (i = kp1; i <= n; ++i) {
     65:       work[i] = aa[i];
     66:       aa[i]   = 0.;
     67:     }
     68:     for (j = kp1; j <= n; ++j) {
     69:       t  = work[j];
     70:       ax = &a[j * n + 1];
     71:       ay = &a[kn + 1];
     72:       for (ll=0; ll<n; ll++) ay[ll] += t*ax[ll];
     73:     }
     74:     l = ipvt[k];
     75:     if (l != k) {
     76:       ax = &a[kn + 1];
     77:       ay = &a[l * n + 1];
     78:       for (ll=0; ll<n; ll++) {
     79:         tmp    = ax[ll];
     80:         ax[ll] = ay[ll];
     81:         ay[ll] = tmp;
     82:       }
     83:     }
     84:   }
     85:   return(0);
     86: }