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: }