Actual source code: dgedi.c

  1: #define PETSCMAT_DLL

  3: /*  
  4:               This file creating by running f2c 
  5:             linpack. this version dated 08/14/78 
  6:       cleve moler, university of new mexico, argonne national lab.

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

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

 15: */

 17:  #include petscsys.h

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

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

 32:    /*     compute inverse(u) */

 34:     for (k = 1; k <= n; ++k) {
 35:         kn           = k*n;
 36:         knp1         = kn + k;
 37:         a[knp1]      = 1.0 / a[knp1];
 38:         t            = -a[knp1];
 39:         i__2         = k - 1;
 40:         aa           = &a[1 + kn];
 41:         for (ll=0; ll<i__2; ll++) aa[ll] *= t;
 42:         kp1 = k + 1;
 43:         if (n < kp1) continue;
 44:         ax = aa;
 45:         for (j = kp1; j <= n; ++j) {
 46:             jn1 = j*n;
 47:             t = a[k + jn1];
 48:             a[k + jn1] = 0.;
 49:             ay = &a[1 + jn1];
 50:             for (ll=0; ll<k; ll++) {
 51:               ay[ll] += t*ax[ll];
 52:             }
 53:         }
 54:     }

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

 58:     nm1 = n - 1;
 59:     if (nm1 < 1) {
 60:         return(0);
 61:     }
 62:     for (kb = 1; kb <= nm1; ++kb) {
 63:         k   = n - kb;
 64:         kn  = k*n;
 65:         kp1 = k + 1;
 66:         aa  = a + kn;
 67:         for (i = kp1; i <= n; ++i) {
 68:             work[i] = aa[i];
 69:             aa[i]   = 0.;
 70:         }
 71:         for (j = kp1; j <= n; ++j) {
 72:             t = work[j];
 73:             ax = &a[j * n + 1];
 74:             ay = &a[kn + 1];
 75:             for (ll=0; ll<n; ll++) {
 76:               ay[ll] += t*ax[ll];
 77:             }
 78:         }
 79:         l = ipvt[k];
 80:         if (l != k) {
 81:             ax = &a[kn + 1];
 82:             ay = &a[l * n + 1];
 83:             for (ll=0; ll<n; ll++) {
 84:               tmp    = ax[ll];
 85:               ax[ll] = ay[ll];
 86:               ay[ll] = tmp;
 87:             }
 88:         }
 89:     }
 90:     return(0);
 91: }