xref: /petsc/src/mat/impls/sbaij/seq/sbaijfact4.c (revision e27a552be151e08936ff7d65f1f2e8dae4b63b83)
1 
2 #include <../src/mat/impls/sbaij/seq/sbaij.h>
3 #include <../src/mat/blockinvert.h>
4 
5 /*
6       Version for when blocks are 3 by 3 Using natural ordering
7 */
8 #undef __FUNCT__
9 #define __FUNCT__ "MatCholeskyFactorNumeric_SeqSBAIJ_3_NaturalOrdering"
10 PetscErrorCode MatCholeskyFactorNumeric_SeqSBAIJ_3_NaturalOrdering(Mat C,Mat A,const MatFactorInfo *info)
11 {
12   Mat_SeqSBAIJ   *a = (Mat_SeqSBAIJ*)A->data,*b = (Mat_SeqSBAIJ *)C->data;
13   PetscErrorCode ierr;
14   PetscInt       i,j,mbs=a->mbs,*bi=b->i,*bj=b->j;
15   PetscInt       *ai,*aj,k,k1,jmin,jmax,*jl,*il,vj,nexti,ili;
16   MatScalar      *ba = b->a,*aa,*ap,*dk,*uik;
17   MatScalar      *u,*diag,*rtmp,*rtmp_ptr;
18   PetscReal      shift = info->shiftamount;
19 
20   PetscFunctionBegin;
21 
22   /* initialization */
23   ierr = PetscMalloc(9*mbs*sizeof(MatScalar),&rtmp);CHKERRQ(ierr);
24   ierr = PetscMemzero(rtmp,9*mbs*sizeof(MatScalar));CHKERRQ(ierr);
25   ierr = PetscMalloc2(mbs,PetscInt,&il,mbs,PetscInt,&jl);CHKERRQ(ierr);
26   for (i=0; i<mbs; i++) {
27     jl[i] = mbs; il[0] = 0;
28   }
29   ierr = PetscMalloc2(9,MatScalar,&dk,9,MatScalar,&uik);CHKERRQ(ierr);
30   ai   = a->i; aj = a->j; aa = a->a;
31 
32   /* for each row k */
33   for (k = 0; k<mbs; k++){
34 
35     /*initialize k-th row with elements nonzero in row k of A */
36     jmin = ai[k]; jmax = ai[k+1];
37     if (jmin < jmax) {
38       ap = aa + jmin*9;
39       for (j = jmin; j < jmax; j++){
40         vj = aj[j];         /* block col. index */
41         rtmp_ptr = rtmp + vj*9;
42         for (i=0; i<9; i++) *rtmp_ptr++ = *ap++;
43       }
44     }
45 
46     /* modify k-th row by adding in those rows i with U(i,k) != 0 */
47     ierr = PetscMemcpy(dk,rtmp+k*9,9*sizeof(MatScalar));CHKERRQ(ierr);
48     i = jl[k]; /* first row to be added to k_th row  */
49 
50     while (i < mbs){
51       nexti = jl[i]; /* next row to be added to k_th row */
52 
53       /* compute multiplier */
54       ili = il[i];  /* index of first nonzero element in U(i,k:bms-1) */
55 
56       /* uik = -inv(Di)*U_bar(i,k) */
57       diag = ba + i*9;
58       u    = ba + ili*9;
59 
60       uik[0] = -(diag[0]*u[0] + diag[3]*u[1] + diag[6]*u[2]);
61       uik[1] = -(diag[1]*u[0] + diag[4]*u[1] + diag[7]*u[2]);
62       uik[2] = -(diag[2]*u[0] + diag[5]*u[1] + diag[8]*u[2]);
63 
64       uik[3] = -(diag[0]*u[3] + diag[3]*u[4] + diag[6]*u[5]);
65       uik[4] = -(diag[1]*u[3] + diag[4]*u[4] + diag[7]*u[5]);
66       uik[5] = -(diag[2]*u[3] + diag[5]*u[4] + diag[8]*u[5]);
67 
68       uik[6] = -(diag[0]*u[6] + diag[3]*u[7] + diag[6]*u[8]);
69       uik[7] = -(diag[1]*u[6] + diag[4]*u[7] + diag[7]*u[8]);
70       uik[8] = -(diag[2]*u[6] + diag[5]*u[7] + diag[8]*u[8]);
71 
72       /* update D(k) += -U(i,k)^T * U_bar(i,k) */
73       dk[0] += uik[0]*u[0] + uik[1]*u[1] + uik[2]*u[2];
74       dk[1] += uik[3]*u[0] + uik[4]*u[1] + uik[5]*u[2];
75       dk[2] += uik[6]*u[0] + uik[7]*u[1] + uik[8]*u[2];
76 
77       dk[3] += uik[0]*u[3] + uik[1]*u[4] + uik[2]*u[5];
78       dk[4] += uik[3]*u[3] + uik[4]*u[4] + uik[5]*u[5];
79       dk[5] += uik[6]*u[3] + uik[7]*u[4] + uik[8]*u[5];
80 
81       dk[6] += uik[0]*u[6] + uik[1]*u[7] + uik[2]*u[8];
82       dk[7] += uik[3]*u[6] + uik[4]*u[7] + uik[5]*u[8];
83       dk[8] += uik[6]*u[6] + uik[7]*u[7] + uik[8]*u[8];
84 
85       ierr = PetscLogFlops(27.0*4.0);CHKERRQ(ierr);
86 
87       /* update -U(i,k) */
88       ierr = PetscMemcpy(ba+ili*9,uik,9*sizeof(MatScalar));CHKERRQ(ierr);
89 
90       /* add multiple of row i to k-th row ... */
91       jmin = ili + 1; jmax = bi[i+1];
92       if (jmin < jmax){
93         for (j=jmin; j<jmax; j++) {
94           /* rtmp += -U(i,k)^T * U_bar(i,j) */
95           rtmp_ptr = rtmp + bj[j]*9;
96           u = ba + j*9;
97           rtmp_ptr[0] += uik[0]*u[0] + uik[1]*u[1] + uik[2]*u[2];
98           rtmp_ptr[1] += uik[3]*u[0] + uik[4]*u[1] + uik[5]*u[2];
99           rtmp_ptr[2] += uik[6]*u[0] + uik[7]*u[1] + uik[8]*u[2];
100 
101           rtmp_ptr[3] += uik[0]*u[3] + uik[1]*u[4] + uik[2]*u[5];
102           rtmp_ptr[4] += uik[3]*u[3] + uik[4]*u[4] + uik[5]*u[5];
103           rtmp_ptr[5] += uik[6]*u[3] + uik[7]*u[4] + uik[8]*u[5];
104 
105           rtmp_ptr[6] += uik[0]*u[6] + uik[1]*u[7] + uik[2]*u[8];
106           rtmp_ptr[7] += uik[3]*u[6] + uik[4]*u[7] + uik[5]*u[8];
107           rtmp_ptr[8] += uik[6]*u[6] + uik[7]*u[7] + uik[8]*u[8];
108         }
109         ierr = PetscLogFlops(2.0*27.0*(jmax-jmin));CHKERRQ(ierr);
110 
111         /* ... add i to row list for next nonzero entry */
112         il[i] = jmin;             /* update il(i) in column k+1, ... mbs-1 */
113         j     = bj[jmin];
114         jl[i] = jl[j]; jl[j] = i; /* update jl */
115       }
116       i = nexti;
117     }
118 
119     /* save nonzero entries in k-th row of U ... */
120 
121     /* invert diagonal block */
122     diag = ba+k*9;
123     ierr = PetscMemcpy(diag,dk,9*sizeof(MatScalar));CHKERRQ(ierr);
124     ierr = Kernel_A_gets_inverse_A_3(diag,shift);CHKERRQ(ierr);
125 
126     jmin = bi[k]; jmax = bi[k+1];
127     if (jmin < jmax) {
128       for (j=jmin; j<jmax; j++){
129          vj = bj[j];           /* block col. index of U */
130          u   = ba + j*9;
131          rtmp_ptr = rtmp + vj*9;
132          for (k1=0; k1<9; k1++){
133            *u++        = *rtmp_ptr;
134            *rtmp_ptr++ = 0.0;
135          }
136       }
137 
138       /* ... add k to row list for first nonzero entry in k-th row */
139       il[k] = jmin;
140       i     = bj[jmin];
141       jl[k] = jl[i]; jl[i] = k;
142     }
143   }
144 
145   ierr = PetscFree(rtmp);CHKERRQ(ierr);
146   ierr = PetscFree2(il,jl);CHKERRQ(ierr);
147   ierr = PetscFree2(dk,uik);CHKERRQ(ierr);
148 
149   C->ops->solve          = MatSolve_SeqSBAIJ_3_NaturalOrdering_inplace;
150   C->ops->solvetranspose = MatSolve_SeqSBAIJ_3_NaturalOrdering_inplace;
151   C->ops->forwardsolve   = MatForwardSolve_SeqSBAIJ_3_NaturalOrdering_inplace;
152   C->ops->backwardsolve  = MatBackwardSolve_SeqSBAIJ_3_NaturalOrdering_inplace;
153 
154   C->assembled = PETSC_TRUE;
155   C->preallocated = PETSC_TRUE;
156   ierr = PetscLogFlops(1.3333*27*b->mbs);CHKERRQ(ierr); /* from inverting diagonal blocks */
157   PetscFunctionReturn(0);
158 }
159