1 /*$Id: sro.c,v 1.26 2001/06/21 21:17:00 bsmith Exp $*/ 2 3 #include "src/mat/impls/baij/seq/baij.h" 4 #include "src/vec/vecimpl.h" 5 #include "src/inline/spops.h" 6 #include "src/mat/impls/sbaij/seq/sbaij.h" 7 #include "petscsys.h" 8 9 /* 10 This function is used before applying a 11 symmetric reordering to matrix A that is 12 in SBAIJ format. 13 14 The permutation is assumed to be symmetric, i.e., 15 P = P^T (= inv(P)), 16 so the permuted matrix P*A*inv(P)=P*A*P^T is ensured to be symmetric. 17 18 The function is modified from sro.f of YSMP. The description from YSMP: 19 C THE NONZERO ENTRIES OF THE MATRIX M ARE ASSUMED TO BE STORED 20 C SYMMETRICALLY IN (IA,JA,A) FORMAT (I.E., NOT BOTH M(I,J) AND M(J,I) 21 C ARE STORED IF I NE J). 22 C 23 C SRO DOES NOT REARRANGE THE ORDER OF THE ROWS, BUT DOES MOVE 24 C NONZEROES FROM ONE ROW TO ANOTHER TO ENSURE THAT IF M(I,J) WILL BE 25 C IN THE UPPER TRIANGLE OF M WITH RESPECT TO THE NEW ORDERING, THEN 26 C M(I,J) IS STORED IN ROW I (AND THUS M(J,I) IS NOT STORED); WHEREAS 27 C IF M(I,J) WILL BE IN THE STRICT LOWER TRIANGLE OF M, THEN M(J,I) IS 28 C STORED IN ROW J (AND THUS M(I,J) IS NOT STORED). 29 30 31 -- output: new index set (inew, jnew) for A and a map a2anew that maps 32 values a to anew, such that all 33 nonzero A_(perm(i),iperm(k)) will be stored in the upper triangle. 34 Note: matrix A is not permuted by this function! 35 */ 36 #undef __FUNCT__ 37 #define __FUNCT__ "MatReorderingSeqSBAIJ" 38 int MatReorderingSeqSBAIJ(Mat A,IS perm) 39 { 40 Mat_SeqSBAIJ *a=(Mat_SeqSBAIJ *)A->data; 41 int *r,ierr,i,mbs=a->mbs,*rip,*riip; 42 int *ai,*aj; 43 int *nzr,nz,jmin,jmax,j,k,ajk,len; 44 IS iperm; /* inverse of perm */ 45 46 PetscFunctionBegin; 47 if (!mbs) PetscFunctionReturn(0); 48 ierr = ISGetIndices(perm,&rip);CHKERRQ(ierr); 49 ierr = ISInvertPermutation(perm,PETSC_DECIDE,&iperm);CHKERRQ(ierr); 50 ierr = ISGetIndices(iperm,&riip);CHKERRQ(ierr); 51 52 for (i=0; i<mbs; i++) { 53 if (rip[i] != riip[i]) SETERRQ(1,"Non-symm. permutation, use symm. permutation or general matrix format"); 54 } 55 ierr = ISRestoreIndices(iperm,&riip);CHKERRQ(ierr); 56 ierr = ISDestroy(iperm);CHKERRQ(ierr); 57 58 if (!a->inew){ 59 len = (mbs+1 + 2*(a->i[mbs]))*sizeof(int); 60 ierr = PetscMalloc(len,&ai);CHKERRQ(ierr); 61 aj = ai + mbs+1; 62 } else { 63 ai = a->inew; aj = a->jnew; 64 } 65 ierr = PetscMemcpy(ai,a->i,(mbs+1)*sizeof(int));CHKERRQ(ierr); 66 ierr = PetscMemcpy(aj,a->j,(a->i[mbs])*sizeof(int));CHKERRQ(ierr); 67 68 /* 69 Phase 1: Find row index r in which to store each nonzero. 70 Initialize count of nonzeros to be stored in each row (nzr). 71 At the end of this phase, a nonzero a(*,*)=a(r(),aj()) 72 s.t. a(perm(r),perm(aj)) will fall into upper triangle part. 73 */ 74 75 ierr = PetscMalloc(mbs*sizeof(int),&nzr);CHKERRQ(ierr); 76 ierr = PetscMalloc(ai[mbs]*sizeof(int),&r);CHKERRQ(ierr); 77 for (i=0; i<mbs; i++) nzr[i] = 0; 78 for (i=0; i<ai[mbs]; i++) r[i] = 0; 79 80 /* for each nonzero element */ 81 for (i=0; i<mbs; i++){ 82 nz = ai[i+1] - ai[i]; 83 j = ai[i]; 84 /* printf("nz = %d, j=%d\n",nz,j); */ 85 while (nz--){ 86 /* --- find row (=r[j]) and column (=aj[j]) in which to store a[j] ...*/ 87 k = aj[j]; /* col. index */ 88 /* printf("nz = %d, k=%d\n", nz,k); */ 89 /* for entry that will be permuted into lower triangle, swap row and col. index */ 90 if (rip[k] < rip[i]) aj[j] = i; 91 else k = i; 92 93 r[j] = k; j++; 94 nzr[k] ++; /* increment count of nonzeros in that row */ 95 } 96 } 97 98 /* Phase 2: Find new ai and permutation to apply to (aj,a). 99 Determine pointers (r) to delimit rows in permuted (aj,a). 100 Note: r is different from r used in phase 1. 101 At the end of this phase, (aj[j],a[j]) will be stored in 102 (aj[r(j)],a[r(j)]). 103 */ 104 for (i=0; i<mbs; i++){ 105 ai[i+1] = ai[i] + nzr[i]; 106 nzr[i] = ai[i+1]; 107 } 108 109 /* determine where each (aj[j], a[j]) is stored in new (aj,a) 110 for each nonzero element (in reverse order) */ 111 jmin = ai[0]; jmax = ai[mbs]; 112 nz = jmax - jmin; 113 j = jmax-1; 114 while (nz--){ 115 i = r[j]; /* row value */ 116 if (aj[j] == i) r[j] = ai[i]; /* put diagonal nonzero at beginning of row */ 117 else { /* put off-diagonal nonzero in last unused location in row */ 118 nzr[i]--; r[j] = nzr[i]; 119 } 120 j--; 121 } 122 123 a->a2anew = aj + ai[mbs]; 124 ierr = PetscMemcpy(a->a2anew,r,ai[mbs]*sizeof(int));CHKERRQ(ierr); 125 126 /* Phase 3: permute (aj,a) to upper triangular form (wrt new ordering) */ 127 for (j=jmin; j<jmax; j++){ 128 while (r[j] != j){ 129 k = r[j]; r[j] = r[k]; r[k] = k; 130 ajk = aj[k]; aj[k] = aj[j]; aj[j] = ajk; 131 /* ak = aa[k]; aa[k] = aa[j]; aa[j] = ak; */ 132 } 133 } 134 ierr= ISRestoreIndices(perm,&rip);CHKERRQ(ierr); 135 136 a->inew = ai; 137 a->jnew = aj; 138 139 if (a->row) { 140 ierr = ISDestroy(a->row);CHKERRQ(ierr); 141 } 142 if (a->icol) { 143 ierr = ISDestroy(a->icol);CHKERRQ(ierr); 144 } 145 a->row = perm; 146 a->icol = perm; 147 ierr = PetscObjectReference((PetscObject)perm);CHKERRQ(ierr); 148 ierr = PetscObjectReference((PetscObject)perm);CHKERRQ(ierr); 149 150 ierr = PetscFree(nzr);CHKERRQ(ierr); 151 ierr = PetscFree(r);CHKERRQ(ierr); 152 153 PetscFunctionReturn(0); 154 } 155 156 157