xref: /petsc/src/mat/impls/sbaij/seq/sbaijfact9.c (revision c56ceb406e7f1e4076bf88d4e7444df54c64fc7a)
1 #include <../src/mat/impls/sbaij/seq/sbaij.h>
2 #include <petsc/private/kernels/blockinvert.h>
3 
4 /* Version for when blocks are 6 by 6 */
MatCholeskyFactorNumeric_SeqSBAIJ_6(Mat C,Mat A,const MatFactorInfo * info)5 PetscErrorCode MatCholeskyFactorNumeric_SeqSBAIJ_6(Mat C, Mat A, const MatFactorInfo *info)
6 {
7   Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ *)A->data, *b = (Mat_SeqSBAIJ *)C->data;
8   IS              perm = b->row;
9   const PetscInt *ai, *aj, *perm_ptr, mbs = a->mbs, *bi = b->i, *bj = b->j;
10   PetscInt        i, j, *a2anew, k, k1, jmin, jmax, *jl, *il, vj, nexti, ili;
11   MatScalar      *ba = b->a, *aa, *ap, *dk, *uik;
12   MatScalar      *u, *d, *w, *wp, u0, u1, u2, u3, u4, u5, u6, u7, u8, u9, u10, u11, u12;
13   MatScalar       u13, u14, u15, u16, u17, u18, u19, u20, u21, u22, u23, u24, u25, u26, u27;
14   MatScalar       u28, u29, u30, u31, u32, u33, u34, u35;
15   PetscReal       shift = info->shiftamount;
16   PetscBool       allowzeropivot, zeropivotdetected;
17 
18   PetscFunctionBegin;
19   /* initialization */
20   allowzeropivot = PetscNot(A->erroriffailure);
21   PetscCall(PetscCalloc1(36 * mbs, &w));
22   PetscCall(PetscMalloc2(mbs, &il, mbs, &jl));
23   il[0] = 0;
24   for (i = 0; i < mbs; i++) jl[i] = mbs;
25 
26   PetscCall(PetscMalloc2(36, &dk, 36, &uik));
27   PetscCall(ISGetIndices(perm, &perm_ptr));
28 
29   /* check permutation */
30   if (!a->permute) {
31     ai = a->i;
32     aj = a->j;
33     aa = a->a;
34   } else {
35     ai = a->inew;
36     aj = a->jnew;
37     PetscCall(PetscMalloc1(36 * ai[mbs], &aa));
38     PetscCall(PetscArraycpy(aa, a->a, 36 * ai[mbs]));
39     PetscCall(PetscMalloc1(ai[mbs], &a2anew));
40     PetscCall(PetscArraycpy(a2anew, a->a2anew, ai[mbs]));
41 
42     for (i = 0; i < mbs; i++) {
43       jmin = ai[i];
44       jmax = ai[i + 1];
45       for (j = jmin; j < jmax; j++) {
46         while (a2anew[j] != j) {
47           k         = a2anew[j];
48           a2anew[j] = a2anew[k];
49           a2anew[k] = k;
50           for (k1 = 0; k1 < 36; k1++) {
51             dk[k1]          = aa[k * 36 + k1];
52             aa[k * 36 + k1] = aa[j * 36 + k1];
53             aa[j * 36 + k1] = dk[k1];
54           }
55         }
56         /* transform column-oriented blocks that lie in the lower triangle to row-oriented blocks */
57         if (i > aj[j]) {
58           /* printf("change orientation, row: %d, col: %d\n",i,aj[j]); */
59           ap = aa + j * 36;                       /* ptr to the beginning of j-th block of aa */
60           for (k = 0; k < 36; k++) dk[k] = ap[k]; /* dk <- j-th block of aa */
61           for (k = 0; k < 6; k++) {               /* j-th block of aa <- dk^T */
62             for (k1 = 0; k1 < 6; k1++) *ap++ = dk[k + 6 * k1];
63           }
64         }
65       }
66     }
67     PetscCall(PetscFree(a2anew));
68   }
69 
70   /* for each row k */
71   for (k = 0; k < mbs; k++) {
72     /*initialize k-th row with elements nonzero in row perm(k) of A */
73     jmin = ai[perm_ptr[k]];
74     jmax = ai[perm_ptr[k] + 1];
75     if (jmin < jmax) {
76       ap = aa + jmin * 36;
77       for (j = jmin; j < jmax; j++) {
78         vj = perm_ptr[aj[j]]; /* block col. index */
79         wp = w + vj * 36;
80         for (i = 0; i < 36; i++) *wp++ = *ap++;
81       }
82     }
83 
84     /* modify k-th row by adding in those rows i with U(i,k) != 0 */
85     PetscCall(PetscArraycpy(dk, w + k * 36, 36));
86     i = jl[k]; /* first row to be added to k_th row  */
87 
88     while (i < mbs) {
89       nexti = jl[i]; /* next row to be added to k_th row */
90 
91       /* compute multiplier */
92       ili = il[i]; /* index of first nonzero element in U(i,k:bms-1) */
93 
94       /* uik = -inv(Di)*U_bar(i,k) */
95       d = ba + i * 36;
96       u = ba + ili * 36;
97 
98       u0  = u[0];
99       u1  = u[1];
100       u2  = u[2];
101       u3  = u[3];
102       u4  = u[4];
103       u5  = u[5];
104       u6  = u[6];
105       u7  = u[7];
106       u8  = u[8];
107       u9  = u[9];
108       u10 = u[10];
109       u11 = u[11];
110       u12 = u[12];
111       u13 = u[13];
112       u14 = u[14];
113       u15 = u[15];
114       u16 = u[16];
115       u17 = u[17];
116       u18 = u[18];
117       u19 = u[19];
118       u20 = u[20];
119       u21 = u[21];
120       u22 = u[22];
121       u23 = u[23];
122       u24 = u[24];
123       u25 = u[25];
124       u26 = u[26];
125       u27 = u[27];
126       u28 = u[28];
127       u29 = u[29];
128       u30 = u[30];
129       u31 = u[31];
130       u32 = u[32];
131       u33 = u[33];
132       u34 = u[34];
133       u35 = u[35];
134 
135       uik[0] = -(d[0] * u0 + d[6] * u1 + d[12] * u2 + d[18] * u3 + d[24] * u4 + d[30] * u5);
136       uik[1] = -(d[1] * u0 + d[7] * u1 + d[13] * u2 + d[19] * u3 + d[25] * u4 + d[31] * u5);
137       uik[2] = -(d[2] * u0 + d[8] * u1 + d[14] * u2 + d[20] * u3 + d[26] * u4 + d[32] * u5);
138       uik[3] = -(d[3] * u0 + d[9] * u1 + d[15] * u2 + d[21] * u3 + d[27] * u4 + d[33] * u5);
139       uik[4] = -(d[4] * u0 + d[10] * u1 + d[16] * u2 + d[22] * u3 + d[28] * u4 + d[34] * u5);
140       uik[5] = -(d[5] * u0 + d[11] * u1 + d[17] * u2 + d[23] * u3 + d[29] * u4 + d[35] * u5);
141 
142       uik[6]  = -(d[0] * u6 + d[6] * u7 + d[12] * u8 + d[18] * u9 + d[24] * u10 + d[30] * u11);
143       uik[7]  = -(d[1] * u6 + d[7] * u7 + d[13] * u8 + d[19] * u9 + d[25] * u10 + d[31] * u11);
144       uik[8]  = -(d[2] * u6 + d[8] * u7 + d[14] * u8 + d[20] * u9 + d[26] * u10 + d[32] * u11);
145       uik[9]  = -(d[3] * u6 + d[9] * u7 + d[15] * u8 + d[21] * u9 + d[27] * u10 + d[33] * u11);
146       uik[10] = -(d[4] * u6 + d[10] * u7 + d[16] * u8 + d[22] * u9 + d[28] * u10 + d[34] * u11);
147       uik[11] = -(d[5] * u6 + d[11] * u7 + d[17] * u8 + d[23] * u9 + d[29] * u10 + d[35] * u11);
148 
149       uik[12] = -(d[0] * u12 + d[6] * u13 + d[12] * u14 + d[18] * u15 + d[24] * u16 + d[30] * u17);
150       uik[13] = -(d[1] * u12 + d[7] * u13 + d[13] * u14 + d[19] * u15 + d[25] * u16 + d[31] * u17);
151       uik[14] = -(d[2] * u12 + d[8] * u13 + d[14] * u14 + d[20] * u15 + d[26] * u16 + d[32] * u17);
152       uik[15] = -(d[3] * u12 + d[9] * u13 + d[15] * u14 + d[21] * u15 + d[27] * u16 + d[33] * u17);
153       uik[16] = -(d[4] * u12 + d[10] * u13 + d[16] * u14 + d[22] * u15 + d[28] * u16 + d[34] * u17);
154       uik[17] = -(d[5] * u12 + d[11] * u13 + d[17] * u14 + d[23] * u15 + d[29] * u16 + d[35] * u17);
155 
156       uik[18] = -(d[0] * u18 + d[6] * u19 + d[12] * u20 + d[18] * u21 + d[24] * u22 + d[30] * u23);
157       uik[19] = -(d[1] * u18 + d[7] * u19 + d[13] * u20 + d[19] * u21 + d[25] * u22 + d[31] * u23);
158       uik[20] = -(d[2] * u18 + d[8] * u19 + d[14] * u20 + d[20] * u21 + d[26] * u22 + d[32] * u23);
159       uik[21] = -(d[3] * u18 + d[9] * u19 + d[15] * u20 + d[21] * u21 + d[27] * u22 + d[33] * u23);
160       uik[22] = -(d[4] * u18 + d[10] * u19 + d[16] * u20 + d[22] * u21 + d[28] * u22 + d[34] * u23);
161       uik[23] = -(d[5] * u18 + d[11] * u19 + d[17] * u20 + d[23] * u21 + d[29] * u22 + d[35] * u23);
162 
163       uik[24] = -(d[0] * u24 + d[6] * u25 + d[12] * u26 + d[18] * u27 + d[24] * u28 + d[30] * u29);
164       uik[25] = -(d[1] * u24 + d[7] * u25 + d[13] * u26 + d[19] * u27 + d[25] * u28 + d[31] * u29);
165       uik[26] = -(d[2] * u24 + d[8] * u25 + d[14] * u26 + d[20] * u27 + d[26] * u28 + d[32] * u29);
166       uik[27] = -(d[3] * u24 + d[9] * u25 + d[15] * u26 + d[21] * u27 + d[27] * u28 + d[33] * u29);
167       uik[28] = -(d[4] * u24 + d[10] * u25 + d[16] * u26 + d[22] * u27 + d[28] * u28 + d[34] * u29);
168       uik[29] = -(d[5] * u24 + d[11] * u25 + d[17] * u26 + d[23] * u27 + d[29] * u28 + d[35] * u29);
169 
170       uik[30] = -(d[0] * u30 + d[6] * u31 + d[12] * u32 + d[18] * u33 + d[24] * u34 + d[30] * u35);
171       uik[31] = -(d[1] * u30 + d[7] * u31 + d[13] * u32 + d[19] * u33 + d[25] * u34 + d[31] * u35);
172       uik[32] = -(d[2] * u30 + d[8] * u31 + d[14] * u32 + d[20] * u33 + d[26] * u34 + d[32] * u35);
173       uik[33] = -(d[3] * u30 + d[9] * u31 + d[15] * u32 + d[21] * u33 + d[27] * u34 + d[33] * u35);
174       uik[34] = -(d[4] * u30 + d[10] * u31 + d[16] * u32 + d[22] * u33 + d[28] * u34 + d[34] * u35);
175       uik[35] = -(d[5] * u30 + d[11] * u31 + d[17] * u32 + d[23] * u33 + d[29] * u34 + d[35] * u35);
176 
177       /* update D(k) += -U(i,k)^T * U_bar(i,k) */
178       dk[0] += uik[0] * u0 + uik[1] * u1 + uik[2] * u2 + uik[3] * u3 + uik[4] * u4 + uik[5] * u5;
179       dk[1] += uik[6] * u0 + uik[7] * u1 + uik[8] * u2 + uik[9] * u3 + uik[10] * u4 + uik[11] * u5;
180       dk[2] += uik[12] * u0 + uik[13] * u1 + uik[14] * u2 + uik[15] * u3 + uik[16] * u4 + uik[17] * u5;
181       dk[3] += uik[18] * u0 + uik[19] * u1 + uik[20] * u2 + uik[21] * u3 + uik[22] * u4 + uik[23] * u5;
182       dk[4] += uik[24] * u0 + uik[25] * u1 + uik[26] * u2 + uik[27] * u3 + uik[28] * u4 + uik[29] * u5;
183       dk[5] += uik[30] * u0 + uik[31] * u1 + uik[32] * u2 + uik[33] * u3 + uik[34] * u4 + uik[35] * u5;
184 
185       dk[6] += uik[0] * u6 + uik[1] * u7 + uik[2] * u8 + uik[3] * u9 + uik[4] * u10 + uik[5] * u11;
186       dk[7] += uik[6] * u6 + uik[7] * u7 + uik[8] * u8 + uik[9] * u9 + uik[10] * u10 + uik[11] * u11;
187       dk[8] += uik[12] * u6 + uik[13] * u7 + uik[14] * u8 + uik[15] * u9 + uik[16] * u10 + uik[17] * u11;
188       dk[9] += uik[18] * u6 + uik[19] * u7 + uik[20] * u8 + uik[21] * u9 + uik[22] * u10 + uik[23] * u11;
189       dk[10] += uik[24] * u6 + uik[25] * u7 + uik[26] * u8 + uik[27] * u9 + uik[28] * u10 + uik[29] * u11;
190       dk[11] += uik[30] * u6 + uik[31] * u7 + uik[32] * u8 + uik[33] * u9 + uik[34] * u10 + uik[35] * u11;
191 
192       dk[12] += uik[0] * u12 + uik[1] * u13 + uik[2] * u14 + uik[3] * u15 + uik[4] * u16 + uik[5] * u17;
193       dk[13] += uik[6] * u12 + uik[7] * u13 + uik[8] * u14 + uik[9] * u15 + uik[10] * u16 + uik[11] * u17;
194       dk[14] += uik[12] * u12 + uik[13] * u13 + uik[14] * u14 + uik[15] * u15 + uik[16] * u16 + uik[17] * u17;
195       dk[15] += uik[18] * u12 + uik[19] * u13 + uik[20] * u14 + uik[21] * u15 + uik[22] * u16 + uik[23] * u17;
196       dk[16] += uik[24] * u12 + uik[25] * u13 + uik[26] * u14 + uik[27] * u15 + uik[28] * u16 + uik[29] * u17;
197       dk[17] += uik[30] * u12 + uik[31] * u13 + uik[32] * u14 + uik[33] * u15 + uik[34] * u16 + uik[35] * u17;
198 
199       dk[18] += uik[0] * u18 + uik[1] * u19 + uik[2] * u20 + uik[3] * u21 + uik[4] * u22 + uik[5] * u23;
200       dk[19] += uik[6] * u18 + uik[7] * u19 + uik[8] * u20 + uik[9] * u21 + uik[10] * u22 + uik[11] * u23;
201       dk[20] += uik[12] * u18 + uik[13] * u19 + uik[14] * u20 + uik[15] * u21 + uik[16] * u22 + uik[17] * u23;
202       dk[21] += uik[18] * u18 + uik[19] * u19 + uik[20] * u20 + uik[21] * u21 + uik[22] * u22 + uik[23] * u23;
203       dk[22] += uik[24] * u18 + uik[25] * u19 + uik[26] * u20 + uik[27] * u21 + uik[28] * u22 + uik[29] * u23;
204       dk[23] += uik[30] * u18 + uik[31] * u19 + uik[32] * u20 + uik[33] * u21 + uik[34] * u22 + uik[35] * u23;
205 
206       dk[24] += uik[0] * u24 + uik[1] * u25 + uik[2] * u26 + uik[3] * u27 + uik[4] * u28 + uik[5] * u29;
207       dk[25] += uik[6] * u24 + uik[7] * u25 + uik[8] * u26 + uik[9] * u27 + uik[10] * u28 + uik[11] * u29;
208       dk[26] += uik[12] * u24 + uik[13] * u25 + uik[14] * u26 + uik[15] * u27 + uik[16] * u28 + uik[17] * u29;
209       dk[27] += uik[18] * u24 + uik[19] * u25 + uik[20] * u26 + uik[21] * u27 + uik[22] * u28 + uik[23] * u29;
210       dk[28] += uik[24] * u24 + uik[25] * u25 + uik[26] * u26 + uik[27] * u27 + uik[28] * u28 + uik[29] * u29;
211       dk[29] += uik[30] * u24 + uik[31] * u25 + uik[32] * u26 + uik[33] * u27 + uik[34] * u28 + uik[35] * u29;
212 
213       dk[30] += uik[0] * u30 + uik[1] * u31 + uik[2] * u32 + uik[3] * u33 + uik[4] * u34 + uik[5] * u35;
214       dk[31] += uik[6] * u30 + uik[7] * u31 + uik[8] * u32 + uik[9] * u33 + uik[10] * u34 + uik[11] * u35;
215       dk[32] += uik[12] * u30 + uik[13] * u31 + uik[14] * u32 + uik[15] * u33 + uik[16] * u34 + uik[17] * u35;
216       dk[33] += uik[18] * u30 + uik[19] * u31 + uik[20] * u32 + uik[21] * u33 + uik[22] * u34 + uik[23] * u35;
217       dk[34] += uik[24] * u30 + uik[25] * u31 + uik[26] * u32 + uik[27] * u33 + uik[28] * u34 + uik[29] * u35;
218       dk[35] += uik[30] * u30 + uik[31] * u31 + uik[32] * u32 + uik[33] * u33 + uik[34] * u34 + uik[35] * u35;
219 
220       PetscCall(PetscLogFlops(216.0 * 4.0));
221 
222       /* update -U(i,k) */
223       PetscCall(PetscArraycpy(ba + ili * 36, uik, 36));
224 
225       /* add multiple of row i to k-th row ... */
226       jmin = ili + 1;
227       jmax = bi[i + 1];
228       if (jmin < jmax) {
229         for (j = jmin; j < jmax; j++) {
230           /* w += -U(i,k)^T * U_bar(i,j) */
231           wp = w + bj[j] * 36;
232           u  = ba + j * 36;
233 
234           u0  = u[0];
235           u1  = u[1];
236           u2  = u[2];
237           u3  = u[3];
238           u4  = u[4];
239           u5  = u[5];
240           u6  = u[6];
241           u7  = u[7];
242           u8  = u[8];
243           u9  = u[9];
244           u10 = u[10];
245           u11 = u[11];
246           u12 = u[12];
247           u13 = u[13];
248           u14 = u[14];
249           u15 = u[15];
250           u16 = u[16];
251           u17 = u[17];
252           u18 = u[18];
253           u19 = u[19];
254           u20 = u[20];
255           u21 = u[21];
256           u22 = u[22];
257           u23 = u[23];
258           u24 = u[24];
259           u25 = u[25];
260           u26 = u[26];
261           u27 = u[27];
262           u28 = u[28];
263           u29 = u[29];
264           u30 = u[30];
265           u31 = u[31];
266           u32 = u[32];
267           u33 = u[33];
268           u34 = u[34];
269           u35 = u[35];
270 
271           wp[0] += uik[0] * u0 + uik[1] * u1 + uik[2] * u2 + uik[3] * u3 + uik[4] * u4 + uik[5] * u5;
272           wp[1] += uik[6] * u0 + uik[7] * u1 + uik[8] * u2 + uik[9] * u3 + uik[10] * u4 + uik[11] * u5;
273           wp[2] += uik[12] * u0 + uik[13] * u1 + uik[14] * u2 + uik[15] * u3 + uik[16] * u4 + uik[17] * u5;
274           wp[3] += uik[18] * u0 + uik[19] * u1 + uik[20] * u2 + uik[21] * u3 + uik[22] * u4 + uik[23] * u5;
275           wp[4] += uik[24] * u0 + uik[25] * u1 + uik[26] * u2 + uik[27] * u3 + uik[28] * u4 + uik[29] * u5;
276           wp[5] += uik[30] * u0 + uik[31] * u1 + uik[32] * u2 + uik[33] * u3 + uik[34] * u4 + uik[35] * u5;
277 
278           wp[6] += uik[0] * u6 + uik[1] * u7 + uik[2] * u8 + uik[3] * u9 + uik[4] * u10 + uik[5] * u11;
279           wp[7] += uik[6] * u6 + uik[7] * u7 + uik[8] * u8 + uik[9] * u9 + uik[10] * u10 + uik[11] * u11;
280           wp[8] += uik[12] * u6 + uik[13] * u7 + uik[14] * u8 + uik[15] * u9 + uik[16] * u10 + uik[17] * u11;
281           wp[9] += uik[18] * u6 + uik[19] * u7 + uik[20] * u8 + uik[21] * u9 + uik[22] * u10 + uik[23] * u11;
282           wp[10] += uik[24] * u6 + uik[25] * u7 + uik[26] * u8 + uik[27] * u9 + uik[28] * u10 + uik[29] * u11;
283           wp[11] += uik[30] * u6 + uik[31] * u7 + uik[32] * u8 + uik[33] * u9 + uik[34] * u10 + uik[35] * u11;
284 
285           wp[12] += uik[0] * u12 + uik[1] * u13 + uik[2] * u14 + uik[3] * u15 + uik[4] * u16 + uik[5] * u17;
286           wp[13] += uik[6] * u12 + uik[7] * u13 + uik[8] * u14 + uik[9] * u15 + uik[10] * u16 + uik[11] * u17;
287           wp[14] += uik[12] * u12 + uik[13] * u13 + uik[14] * u14 + uik[15] * u15 + uik[16] * u16 + uik[17] * u17;
288           wp[15] += uik[18] * u12 + uik[19] * u13 + uik[20] * u14 + uik[21] * u15 + uik[22] * u16 + uik[23] * u17;
289           wp[16] += uik[24] * u12 + uik[25] * u13 + uik[26] * u14 + uik[27] * u15 + uik[28] * u16 + uik[29] * u17;
290           wp[17] += uik[30] * u12 + uik[31] * u13 + uik[32] * u14 + uik[33] * u15 + uik[34] * u16 + uik[35] * u17;
291 
292           wp[18] += uik[0] * u18 + uik[1] * u19 + uik[2] * u20 + uik[3] * u21 + uik[4] * u22 + uik[5] * u23;
293           wp[19] += uik[6] * u18 + uik[7] * u19 + uik[8] * u20 + uik[9] * u21 + uik[10] * u22 + uik[11] * u23;
294           wp[20] += uik[12] * u18 + uik[13] * u19 + uik[14] * u20 + uik[15] * u21 + uik[16] * u22 + uik[17] * u23;
295           wp[21] += uik[18] * u18 + uik[19] * u19 + uik[20] * u20 + uik[21] * u21 + uik[22] * u22 + uik[23] * u23;
296           wp[22] += uik[24] * u18 + uik[25] * u19 + uik[26] * u20 + uik[27] * u21 + uik[28] * u22 + uik[29] * u23;
297           wp[23] += uik[30] * u18 + uik[31] * u19 + uik[32] * u20 + uik[33] * u21 + uik[34] * u22 + uik[35] * u23;
298 
299           wp[24] += uik[0] * u24 + uik[1] * u25 + uik[2] * u26 + uik[3] * u27 + uik[4] * u28 + uik[5] * u29;
300           wp[25] += uik[6] * u24 + uik[7] * u25 + uik[8] * u26 + uik[9] * u27 + uik[10] * u28 + uik[11] * u29;
301           wp[26] += uik[12] * u24 + uik[13] * u25 + uik[14] * u26 + uik[15] * u27 + uik[16] * u28 + uik[17] * u29;
302           wp[27] += uik[18] * u24 + uik[19] * u25 + uik[20] * u26 + uik[21] * u27 + uik[22] * u28 + uik[23] * u29;
303           wp[28] += uik[24] * u24 + uik[25] * u25 + uik[26] * u26 + uik[27] * u27 + uik[28] * u28 + uik[29] * u29;
304           wp[29] += uik[30] * u24 + uik[31] * u25 + uik[32] * u26 + uik[33] * u27 + uik[34] * u28 + uik[35] * u29;
305 
306           wp[30] += uik[0] * u30 + uik[1] * u31 + uik[2] * u32 + uik[3] * u33 + uik[4] * u34 + uik[5] * u35;
307           wp[31] += uik[6] * u30 + uik[7] * u31 + uik[8] * u32 + uik[9] * u33 + uik[10] * u34 + uik[11] * u35;
308           wp[32] += uik[12] * u30 + uik[13] * u31 + uik[14] * u32 + uik[15] * u33 + uik[16] * u34 + uik[17] * u35;
309           wp[33] += uik[18] * u30 + uik[19] * u31 + uik[20] * u32 + uik[21] * u33 + uik[22] * u34 + uik[23] * u35;
310           wp[34] += uik[24] * u30 + uik[25] * u31 + uik[26] * u32 + uik[27] * u33 + uik[28] * u34 + uik[29] * u35;
311           wp[35] += uik[30] * u30 + uik[31] * u31 + uik[32] * u32 + uik[33] * u33 + uik[34] * u34 + uik[35] * u35;
312         }
313         PetscCall(PetscLogFlops(2.0 * 216.0 * (jmax - jmin)));
314 
315         /* ... add i to row list for next nonzero entry */
316         il[i] = jmin; /* update il(i) in column k+1, ... mbs-1 */
317         j     = bj[jmin];
318         jl[i] = jl[j];
319         jl[j] = i; /* update jl */
320       }
321       i = nexti;
322     }
323 
324     /* save nonzero entries in k-th row of U ... */
325 
326     /* invert diagonal block */
327     d = ba + k * 36;
328     PetscCall(PetscArraycpy(d, dk, 36));
329     PetscCall(PetscKernel_A_gets_inverse_A_6(d, shift, allowzeropivot, &zeropivotdetected));
330     if (zeropivotdetected) C->factorerrortype = MAT_FACTOR_NUMERIC_ZEROPIVOT;
331 
332     jmin = bi[k];
333     jmax = bi[k + 1];
334     if (jmin < jmax) {
335       for (j = jmin; j < jmax; j++) {
336         vj = bj[j]; /* block col. index of U */
337         u  = ba + j * 36;
338         wp = w + vj * 36;
339         for (k1 = 0; k1 < 36; k1++) {
340           *u++  = *wp;
341           *wp++ = 0.0;
342         }
343       }
344 
345       /* ... add k to row list for first nonzero entry in k-th row */
346       il[k] = jmin;
347       i     = bj[jmin];
348       jl[k] = jl[i];
349       jl[i] = k;
350     }
351   }
352 
353   PetscCall(PetscFree(w));
354   PetscCall(PetscFree2(il, jl));
355   PetscCall(PetscFree2(dk, uik));
356   if (a->permute) PetscCall(PetscFree(aa));
357 
358   PetscCall(ISRestoreIndices(perm, &perm_ptr));
359 
360   C->ops->solve          = MatSolve_SeqSBAIJ_6_inplace;
361   C->ops->solvetranspose = MatSolve_SeqSBAIJ_6_inplace;
362   C->assembled           = PETSC_TRUE;
363   C->preallocated        = PETSC_TRUE;
364 
365   PetscCall(PetscLogFlops(1.3333 * 216 * b->mbs)); /* from inverting diagonal blocks */
366   PetscFunctionReturn(PETSC_SUCCESS);
367 }
368