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>
 17: #include <petsc/private/kernels/blockinvert.h>

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

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

 30:   /*     compute inverse(u) */

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

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

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