Actual source code: dgefa7.c
1: #define PETSCMAT_DLL
3: /*
4: Inverts 7 by 7 matrix using partial pivoting.
6: Used by the sparse factorization routines in
7: src/mat/impls/baij/seq and src/mat/impls/bdiag/seq
9: See also src/inline/ilu.h
11: This is a combination of the Linpack routines
12: dgefa() and dgedi() specialized for a size of 7.
14: */
15: #include petsc.h
19: PetscErrorCode Kernel_A_gets_inverse_A_7(MatScalar *a)
20: {
21: PetscInt i__2,i__3,kp1,j,k,l,ll,i,ipvt[7],kb,k3;
22: PetscInt k4,j3;
23: MatScalar *aa,*ax,*ay,work[49],stmp;
24: MatReal tmp,max;
26: /* gaussian elimination with partial pivoting */
29: /* Parameter adjustments */
30: a -= 8;
32: for (k = 1; k <= 6; ++k) {
33: kp1 = k + 1;
34: k3 = 7*k;
35: k4 = k3 + k;
36: /* find l = pivot index */
38: i__2 = 7 - k;
39: aa = &a[k4];
40: max = PetscAbsScalar(aa[0]);
41: l = 1;
42: for (ll=1; ll<i__2; ll++) {
43: tmp = PetscAbsScalar(aa[ll]);
44: if (tmp > max) { max = tmp; l = ll+1;}
45: }
46: l += k - 1;
47: ipvt[k-1] = l;
49: if (a[l + k3] == 0.0) {
50: SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",k-1);
51: }
53: /* interchange if necessary */
55: if (l != k) {
56: stmp = a[l + k3];
57: a[l + k3] = a[k4];
58: a[k4] = stmp;
59: }
61: /* compute multipliers */
63: stmp = -1. / a[k4];
64: i__2 = 7 - k;
65: aa = &a[1 + k4];
66: for (ll=0; ll<i__2; ll++) {
67: aa[ll] *= stmp;
68: }
70: /* row elimination with column indexing */
72: ax = &a[k4+1];
73: for (j = kp1; j <= 7; ++j) {
74: j3 = 7*j;
75: stmp = a[l + j3];
76: if (l != k) {
77: a[l + j3] = a[k + j3];
78: a[k + j3] = stmp;
79: }
81: i__3 = 7 - k;
82: ay = &a[1+k+j3];
83: for (ll=0; ll<i__3; ll++) {
84: ay[ll] += stmp*ax[ll];
85: }
86: }
87: }
88: ipvt[6] = 7;
89: if (a[56] == 0.0) {
90: SETERRQ1(PETSC_ERR_MAT_LU_ZRPVT,"Zero pivot, row %D",6);
91: }
93: /*
94: Now form the inverse
95: */
97: /* compute inverse(u) */
99: for (k = 1; k <= 7; ++k) {
100: k3 = 7*k;
101: k4 = k3 + k;
102: a[k4] = 1.0 / a[k4];
103: stmp = -a[k4];
104: i__2 = k - 1;
105: aa = &a[k3 + 1];
106: for (ll=0; ll<i__2; ll++) aa[ll] *= stmp;
107: kp1 = k + 1;
108: if (7 < kp1) continue;
109: ax = aa;
110: for (j = kp1; j <= 7; ++j) {
111: j3 = 7*j;
112: stmp = a[k + j3];
113: a[k + j3] = 0.0;
114: ay = &a[j3 + 1];
115: for (ll=0; ll<k; ll++) {
116: ay[ll] += stmp*ax[ll];
117: }
118: }
119: }
121: /* form inverse(u)*inverse(l) */
123: for (kb = 1; kb <= 6; ++kb) {
124: k = 7 - kb;
125: k3 = 7*k;
126: kp1 = k + 1;
127: aa = a + k3;
128: for (i = kp1; i <= 7; ++i) {
129: work[i-1] = aa[i];
130: aa[i] = 0.0;
131: }
132: for (j = kp1; j <= 7; ++j) {
133: stmp = work[j-1];
134: ax = &a[7*j + 1];
135: ay = &a[k3 + 1];
136: ay[0] += stmp*ax[0];
137: ay[1] += stmp*ax[1];
138: ay[2] += stmp*ax[2];
139: ay[3] += stmp*ax[3];
140: ay[4] += stmp*ax[4];
141: ay[5] += stmp*ax[5];
142: ay[6] += stmp*ax[6];
143: }
144: l = ipvt[k-1];
145: if (l != k) {
146: ax = &a[k3 + 1];
147: ay = &a[7*l + 1];
148: stmp = ax[0]; ax[0] = ay[0]; ay[0] = stmp;
149: stmp = ax[1]; ax[1] = ay[1]; ay[1] = stmp;
150: stmp = ax[2]; ax[2] = ay[2]; ay[2] = stmp;
151: stmp = ax[3]; ax[3] = ay[3]; ay[3] = stmp;
152: stmp = ax[4]; ax[4] = ay[4]; ay[4] = stmp;
153: stmp = ax[5]; ax[5] = ay[5]; ay[5] = stmp;
154: stmp = ax[6]; ax[6] = ay[6]; ay[6] = stmp;
155: }
156: }
157: return(0);
158: }