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//------------------------------------------------------------------------------
// CCOLAMD/Demo/ccolamd_example: simple example for CCOLAMD
//------------------------------------------------------------------------------
// CCOLAMD, Copyright (c) 2005-2022, Univ. of Florida, All Rights Reserved.
// Authors: Timothy A. Davis, Sivasankaran Rajamanickam, and Stefan Larimore.
// SPDX-License-Identifier: BSD-3-clause
//------------------------------------------------------------------------------
/*
* ccolamd example of use, to order the columns of a 5-by-4 matrix with
* 11 nonzero entries in the following nonzero pattern, with default knobs
* and no ordering constraints.
*
* x 0 x 0
* x 0 x x
* 0 x x 0
* 0 0 x x
* x x 0 0
*
* csymamd example of use, to order the rows and columns of a 5-by-5
* matrix with 13 nonzero entries in the following nonzero pattern,
* with default knobs and no ordering constraints.
*
* x x 0 0 0
* x x x x 0
* 0 x x 0 0
* 0 x 0 x x
* 0 0 0 x x
*
* (where x denotes a nonzero value).
*/
/* ========================================================================== */
#include <stdio.h>
#include "ccolamd.h"
#define A_NNZ 11
#define A_NROW 5
#define A_NCOL 4
#define ALEN 150 /* size max (2.2*nnz+17*ncol+7*nrow+6, 23*ncol+7*nrow+6) */
#define B_NNZ 4
#define B_N 5
int main (void)
{
/* ====================================================================== */
/* input matrix A definition */
/* ====================================================================== */
int A [ALEN] = {
0, 1, 4, /* row indices of nonzeros in column 0 */
2, 4, /* row indices of nonzeros in column 1 */
0, 1, 2, 3, /* row indices of nonzeros in column 2 */
1, 3} ; /* row indices of nonzeros in column 3 */
int p [ ] = {
0, /* column 0 is in A [0..2] */
3, /* column 1 is in A [3..4] */
5, /* column 2 is in A [5..8] */
9, /* column 3 is in A [9..10] */
A_NNZ} ; /* number of nonzeros in A */
/* ====================================================================== */
/* input matrix B definition */
/* ====================================================================== */
int B [ ] = { /* Note: only strictly lower triangular part */
/* is included, since symamd ignores the */
/* diagonal and upper triangular part of B. */
1, /* row indices of nonzeros in column 0 */
2, 3, /* row indices of nonzeros in column 1 */
/* row indices of nonzeros in column 2 (none) */
4 /* row indices of nonzeros in column 3 */
} ; /* row indices of nonzeros in column 4 (none) */
int q [ ] = {
0, /* column 0 is in B [0] */
1, /* column 1 is in B [1..2] */
3, /* column 2 is empty */
3, /* column 3 is in B [3] */
4, /* column 4 is empty */
B_NNZ} ; /* number of nonzeros in strictly lower B */
/* ====================================================================== */
/* other variable definitions */
/* ====================================================================== */
int perm [B_N+1] ; /* note the size is N+1 */
int stats [CCOLAMD_STATS] ; /* for ccolamd and csymamd output statistics */
int row, col, pp, length, ok ;
//--------------------------------------------------------------------------
// ccolamd version
//--------------------------------------------------------------------------
int version [3] ;
ccolamd_version (version) ;
printf ("CCOLAMD v%d.%d.%d\n", version [0], version [1], version [2]) ;
if ((version [0] != CCOLAMD_MAIN_VERSION) ||
(version [1] != CCOLAMD_SUB_VERSION) ||
(version [2] != CCOLAMD_SUBSUB_VERSION))
{
fprintf (stderr, "version in header does not match library\n") ;
abort ( ) ;
}
/* ====================================================================== */
/* dump the input matrix A */
/* ====================================================================== */
printf ("ccolamd %d-by-%d input matrix:\n", A_NROW, A_NCOL) ;
for (col = 0 ; col < A_NCOL ; col++)
{
length = p [col+1] - p [col] ;
printf ("Column %d, with %d entries:\n", col, length) ;
for (pp = p [col] ; pp < p [col+1] ; pp++)
{
row = A [pp] ;
printf (" row %d\n", row) ;
}
}
/* ====================================================================== */
/* order the matrix. Note that this destroys A and overwrites p */
/* ====================================================================== */
ok = ccolamd (A_NROW, A_NCOL, ALEN, A, p, (double *) NULL, stats, NULL) ;
ccolamd_report (stats) ;
if (!ok)
{
printf ("ccolamd error!\n") ;
exit (1) ;
}
/* ====================================================================== */
/* print the column ordering */
/* ====================================================================== */
printf ("ccolamd column ordering:\n") ;
printf ("1st column: %d\n", p [0]) ;
printf ("2nd column: %d\n", p [1]) ;
printf ("3rd column: %d\n", p [2]) ;
printf ("4th column: %d\n", p [3]) ;
/* ====================================================================== */
/* dump the strictly lower triangular part of symmetric input matrix B */
/* ====================================================================== */
printf ("\n\ncsymamd %d-by-%d input matrix:\n", B_N, B_N) ;
printf ("Entries in strictly lower triangular part:\n") ;
for (col = 0 ; col < B_N ; col++)
{
length = q [col+1] - q [col] ;
printf ("Column %d, with %d entries:\n", col, length) ;
for (pp = q [col] ; pp < q [col+1] ; pp++)
{
row = B [pp] ;
printf (" row %d\n", row) ;
}
}
/* ====================================================================== */
/* order the matrix B. Note that this does not modify B or q. */
/* ====================================================================== */
ok = csymamd (B_N, B, q, perm, (double *) NULL, stats, &calloc, &free,
NULL, -1) ;
csymamd_report (stats) ;
if (!ok)
{
printf ("csymamd error!\n") ;
exit (1) ;
}
/* ====================================================================== */
/* print the symmetric ordering */
/* ====================================================================== */
printf ("csymamd column ordering:\n") ;
printf ("1st row/column: %d\n", perm [0]) ;
printf ("2nd row/column: %d\n", perm [1]) ;
printf ("3rd row/column: %d\n", perm [2]) ;
printf ("4th row/column: %d\n", perm [3]) ;
printf ("5th row/column: %d\n", perm [4]) ;
return (0) ;
}
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