GLOBAL Int CAMD_valid
(
/* inputs, not modified on output: */
Int n_row, /* A is n_row-by-n_col */
Int n_col,
const Int Ap [ ], /* column pointers of A, of size n_col+1 */
const Int Ai [ ] /* row indices of A, of size nz = Ap [n_col] */
)
{
Int nz, j, p1, p2, ilast, i, p, result = CAMD_OK ;
if (n_row < 0 || n_col < 0 || Ap == NULL || Ai == NULL)
{
return (CAMD_INVALID) ;
}
nz = Ap [n_col] ;
if (Ap [0] != 0 || nz < 0)
{
/* column pointers must start at Ap [0] = 0, and Ap [n] must be >= 0 */
CAMD_DEBUG0 (("column 0 pointer bad or nz < 0\n")) ;
return (CAMD_INVALID) ;
}
for (j = 0 ; j < n_col ; j++)
{
p1 = Ap [j] ;
p2 = Ap [j+1] ;
CAMD_DEBUG2 (("\nColumn: "ID" p1: "ID" p2: "ID"\n", j, p1, p2)) ;
if (p1 > p2)
{
/* column pointers must be ascending */
CAMD_DEBUG0 (("column "ID" pointer bad\n", j)) ;
return (CAMD_INVALID) ;
}
ilast = EMPTY ;
for (p = p1 ; p < p2 ; p++)
{
i = Ai [p] ;
CAMD_DEBUG3 (("row: "ID"\n", i)) ;
if (i < 0 || i >= n_row)
{
/* row index out of range */
CAMD_DEBUG0 (("index out of range, col "ID" row "ID"\n", j, i));
return (CAMD_INVALID) ;
}
if (i <= ilast)
{
/* row index unsorted, or duplicate entry present */
CAMD_DEBUG1 (("index unsorted/dupl col "ID" row "ID"\n", j, i));
result = CAMD_OK_BUT_JUMBLED ;
}
ilast = i ;
}
}
return (result) ;
}
GLOBAL size_t CAMD(aat) /* returns nz in A+A' */
(
Int n,
const Int Ap [ ],
const Int Ai [ ],
Int Len [ ], /* Len [j]: length of column j of A+A', excl diagonal*/
Int Tp [ ], /* workspace of size n */
double Info [ ]
)
{
Int p1, p2, p, i, j, pj, pj2, k, nzdiag, nzboth, nz ;
double sym ;
size_t nzaat ;
#ifndef NDEBUG
CAMD_debug_init ("CAMD AAT") ;
for (k = 0 ; k < n ; k++) Tp [k] = EMPTY ;
ASSERT (CAMD(valid) (n, n, Ap, Ai) == CAMD_OK) ;
#endif
if (Info != (double *) NULL)
{
/* clear the Info array, if it exists */
for (i = 0 ; i < CAMD_INFO ; i++)
{
Info [i] = EMPTY ;
}
Info [CAMD_STATUS] = CAMD_OK ;
}
for (k = 0 ; k < n ; k++)
{
Len [k] = 0 ;
}
nzdiag = 0 ;
nzboth = 0 ;
nz = Ap [n] ;
for (k = 0 ; k < n ; k++)
{
p1 = Ap [k] ;
p2 = Ap [k+1] ;
CAMD_DEBUG2 (("\nAAT Column: "ID" p1: "ID" p2: "ID"\n", k, p1, p2)) ;
/* construct A+A' */
for (p = p1 ; p < p2 ; )
{
/* scan the upper triangular part of A */
j = Ai [p] ;
if (j < k)
{
/* entry A (j,k) is in the strictly upper triangular part,
* add both A (j,k) and A (k,j) to the matrix A+A' */
Len [j]++ ;
Len [k]++ ;
CAMD_DEBUG3 ((" upper ("ID","ID") ("ID","ID")\n", j,k, k,j));
p++ ;
}
else if (j == k)
{
/* skip the diagonal */
p++ ;
nzdiag++ ;
break ;
}
else /* j > k */
{
/* first entry below the diagonal */
break ;
}
/* scan lower triangular part of A, in column j until reaching
* row k. Start where last scan left off. */
ASSERT (Tp [j] != EMPTY) ;
ASSERT (Ap [j] <= Tp [j] && Tp [j] <= Ap [j+1]) ;
pj2 = Ap [j+1] ;
for (pj = Tp [j] ; pj < pj2 ; )
{
i = Ai [pj] ;
if (i < k)
{
/* A (i,j) is only in the lower part, not in upper.
* add both A (i,j) and A (j,i) to the matrix A+A' */
Len [i]++ ;
Len [j]++ ;
CAMD_DEBUG3 ((" lower ("ID","ID") ("ID","ID")\n",
i,j, j,i)) ;
pj++ ;
}
else if (i == k)
{
/* entry A (k,j) in lower part and A (j,k) in upper */
pj++ ;
nzboth++ ;
break ;
}
else /* i > k */
{
/* consider this entry later, when k advances to i */
break ;
}
}
Tp [j] = pj ;
}
/* Tp [k] points to the entry just below the diagonal in column k */
Tp [k] = p ;
}
/* clean up, for remaining mismatched entries */
for (j = 0 ; j < n ; j++)
{
for (pj = Tp [j] ; pj < Ap [j+1] ; pj++)
{
i = Ai [pj] ;
/* A (i,j) is only in the lower part, not in upper.
* add both A (i,j) and A (j,i) to the matrix A+A' */
Len [i]++ ;
Len [j]++ ;
CAMD_DEBUG3 ((" lower cleanup ("ID","ID") ("ID","ID")\n",
i,j, j,i)) ;
}
}
/* --------------------------------------------------------------------- */
/* compute the symmetry of the nonzero pattern of A */
/* --------------------------------------------------------------------- */
/* Given a matrix A, the symmetry of A is:
* B = tril (spones (A), -1) + triu (spones (A), 1) ;
* sym = nnz (B & B') / nnz (B) ;
* or 1 if nnz (B) is zero.
*/
if (nz == nzdiag)
{
sym = 1 ;
}
else
{
sym = (2 * (double) nzboth) / ((double) (nz - nzdiag)) ;
}
nzaat = 0 ;
for (k = 0 ; k < n ; k++)
{
nzaat += Len [k] ;
}
CAMD_DEBUG1 (("CAMD nz in A+A', excluding diagonal (nzaat) = %g\n",
(double) nzaat)) ;
CAMD_DEBUG1 ((" nzboth: "ID" nz: "ID" nzdiag: "ID" symmetry: %g\n",
nzboth, nz, nzdiag, sym)) ;
if (Info != (double *) NULL)
{
Info [CAMD_STATUS] = CAMD_OK ;
Info [CAMD_N] = n ;
Info [CAMD_NZ] = nz ;
Info [CAMD_SYMMETRY] = sym ; /* symmetry of pattern of A */
Info [CAMD_NZDIAG] = nzdiag ; /* nonzeros on diagonal of A */
Info [CAMD_NZ_A_PLUS_AT] = nzaat ; /* nonzeros in A+A' */
}
return (nzaat) ;
}
