1 /*
2 This routine was converted by f2c from Linpack source
3 linpack. this version dated 08/14/78
4 cleve moler, university of new mexico, argonne national lab.
5
6 Does an LU factorization with partial pivoting of a dense
7 n by n matrix.
8
9 Used by the sparse factorization routines in
10 src/mat/impls/baij/seq
11
12 */
13 #include <petsc/private/kernels/blockinvert.h>
14
PetscLINPACKgefa(MatScalar * a,PetscInt n,PetscInt * ipvt,PetscBool allowzeropivot,PetscBool * zeropivotdetected)15 PetscErrorCode PetscLINPACKgefa(MatScalar *a, PetscInt n, PetscInt *ipvt, PetscBool allowzeropivot, PetscBool *zeropivotdetected)
16 {
17 PetscInt i__2, i__3, kp1, nm1, j, k, l, ll, kn, knp1, jn1;
18 MatScalar t, *ax, *ay, *aa;
19 MatReal tmp, max;
20
21 PetscFunctionBegin;
22 if (zeropivotdetected) *zeropivotdetected = PETSC_FALSE;
23
24 /* Parameter adjustments */
25 --ipvt;
26 a -= n + 1;
27
28 /* Function Body */
29 nm1 = n - 1;
30 for (k = 1; k <= nm1; ++k) {
31 kp1 = k + 1;
32 kn = k * n;
33 knp1 = k * n + k;
34
35 /* find l = pivot index */
36
37 i__2 = n - k + 1;
38 aa = &a[knp1];
39 max = PetscAbsScalar(aa[0]);
40 l = 1;
41 for (ll = 1; ll < i__2; ll++) {
42 tmp = PetscAbsScalar(aa[ll]);
43 if (tmp > max) {
44 max = tmp;
45 l = ll + 1;
46 }
47 }
48 l += k - 1;
49 ipvt[k] = l;
50
51 if (a[l + kn] == 0.0) {
52 PetscCheck(allowzeropivot, PETSC_COMM_SELF, PETSC_ERR_MAT_LU_ZRPVT, "Zero pivot, row %" PetscInt_FMT, k - 1);
53 PetscCall(PetscInfo(NULL, "Zero pivot, row %" PetscInt_FMT "\n", k - 1));
54 if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE;
55 }
56
57 /* interchange if necessary */
58 if (l != k) {
59 t = a[l + kn];
60 a[l + kn] = a[knp1];
61 a[knp1] = t;
62 }
63
64 /* compute multipliers */
65 t = -1. / a[knp1];
66 i__2 = n - k;
67 aa = &a[1 + knp1];
68 for (ll = 0; ll < i__2; ll++) aa[ll] *= t;
69
70 /* row elimination with column indexing */
71 ax = aa;
72 for (j = kp1; j <= n; ++j) {
73 jn1 = j * n;
74 t = a[l + jn1];
75 if (l != k) {
76 a[l + jn1] = a[k + jn1];
77 a[k + jn1] = t;
78 }
79
80 i__3 = n - k;
81 ay = &a[1 + k + jn1];
82 for (ll = 0; ll < i__3; ll++) ay[ll] += t * ax[ll];
83 }
84 }
85 ipvt[n] = n;
86 if (a[n + n * n] == 0.0) {
87 PetscCheck(allowzeropivot, PETSC_COMM_SELF, PETSC_ERR_MAT_LU_ZRPVT, "Zero pivot, row %" PetscInt_FMT, n - 1);
88 PetscCall(PetscInfo(NULL, "Zero pivot, row %" PetscInt_FMT "\n", n - 1));
89 if (zeropivotdetected) *zeropivotdetected = PETSC_TRUE;
90 }
91 PetscFunctionReturn(PETSC_SUCCESS);
92 }
93