1: /*
  2:               This file creating by running f2c
  3:             linpack. this version dated 08/14/78
  4:       cleve moler, university of new mexico, argonne national lab.

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

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

 13: */

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

 17: PetscErrorCode PetscLINPACKgedi(MatScalar *a, PetscInt n, PetscInt *ipvt, MatScalar *work)
 18: {
 19:   PetscInt   i__2, kb, kp1, nm1, i, j, k, l, ll, kn, knp1, jn1;
 20:   MatScalar *aa, *ax, *ay, tmp;
 21:   MatScalar  t;

 23:   PetscFunctionBegin;
 24:   --work;
 25:   --ipvt;
 26:   a -= n + 1;

 28:   /*     compute inverse(u) */

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

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

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