Actual source code: dgedi.c
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;
25: --work;
26: --ipvt;
27: a -= n + 1;
29: /* compute inverse(u) */
31: for (k = 1; k <= n; ++k) {
32: kn = k * n;
33: knp1 = kn + k;
34: a[knp1] = 1.0 / a[knp1];
35: t = -a[knp1];
36: i__2 = k - 1;
37: aa = &a[1 + kn];
38: for (ll = 0; ll < i__2; ll++) aa[ll] *= t;
39: kp1 = k + 1;
40: if (n < kp1) continue;
41: ax = aa;
42: for (j = kp1; j <= n; ++j) {
43: jn1 = j * n;
44: t = a[k + jn1];
45: a[k + jn1] = 0.;
46: ay = &a[1 + jn1];
47: for (ll = 0; ll < k; ll++) ay[ll] += t * ax[ll];
48: }
49: }
51: /* form inverse(u)*inverse(l) */
53: nm1 = n - 1;
54: if (nm1 < 1) return 0;
55: for (kb = 1; kb <= nm1; ++kb) {
56: k = n - kb;
57: kn = k * n;
58: kp1 = k + 1;
59: aa = a + kn;
60: for (i = kp1; i <= n; ++i) {
61: work[i] = aa[i];
62: aa[i] = 0.;
63: }
64: for (j = kp1; j <= n; ++j) {
65: t = work[j];
66: ax = &a[j * n + 1];
67: ay = &a[kn + 1];
68: for (ll = 0; ll < n; ll++) ay[ll] += t * ax[ll];
69: }
70: l = ipvt[k];
71: if (l != k) {
72: ax = &a[kn + 1];
73: ay = &a[l * n + 1];
74: for (ll = 0; ll < n; ll++) {
75: tmp = ax[ll];
76: ax[ll] = ay[ll];
77: ay[ll] = tmp;
78: }
79: }
80: }
81: return 0;
82: }