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: 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++) {
 50:               ay[ll] += t*ax[ll];
 51:             }
 52:         }
 53:     }

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

 57:     nm1 = n - 1;
 58:     if (nm1 < 1) {
 59:         return(0);
 60:     }
 61:     for (kb = 1; kb <= nm1; ++kb) {
 62:         k   = n - kb;
 63:         kn  = k*n;
 64:         kp1 = k + 1;
 65:         aa  = a + kn;
 66:         for (i = kp1; i <= n; ++i) {
 67:             work[i] = aa[i];
 68:             aa[i]   = 0.;
 69:         }
 70:         for (j = kp1; j <= n; ++j) {
 71:             t = work[j];
 72:             ax = &a[j * n + 1];
 73:             ay = &a[kn + 1];
 74:             for (ll=0; ll<n; ll++) {
 75:               ay[ll] += t*ax[ll];
 76:             }
 77:         }
 78:         l = ipvt[k];
 79:         if (l != k) {
 80:             ax = &a[kn + 1];
 81:             ay = &a[l * n + 1];
 82:             for (ll=0; ll<n; ll++) {
 83:               tmp    = ax[ll];
 84:               ax[ll] = ay[ll];
 85:               ay[ll] = tmp;
 86:             }
 87:         }
 88:     }
 89:     return(0);
 90: }