//------------------------------------------------------------------------------ // COLAMD/Demo/colamd_example.c: simple example for COLAMD //------------------------------------------------------------------------------ // COLAMD, Copyright (c) 1998-2022, Timothy A. Davis and Stefan Larimore, // All Rights Reserved. // SPDX-License-Identifier: BSD-3-clause //------------------------------------------------------------------------------ /* COLAMD / SYMAMD example colamd 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. x 0 x 0 x 0 x x 0 x x 0 0 0 x x x x 0 0 symamd 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. 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 "colamd.h" #define A_NNZ 11 #define A_NROW 5 #define A_NCOL 4 #define ALEN 150 #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 [COLAMD_STATS] ; /* for colamd and symamd output statistics */ int row, col, pp, length, ok ; //-------------------------------------------------------------------------- // colamd version //-------------------------------------------------------------------------- int version [3] ; colamd_version (version) ; printf ("COLAMD v%d.%d.%d\n", version [0], version [1], version [2]) ; if ((version [0] != COLAMD_MAIN_VERSION) || (version [1] != COLAMD_SUB_VERSION) || (version [2] != COLAMD_SUBSUB_VERSION)) { fprintf (stderr, "version in header does not match library\n") ; abort ( ) ; } /* ====================================================================== */ /* dump the input matrix A */ /* ====================================================================== */ printf ("colamd %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 = colamd (A_NROW, A_NCOL, ALEN, A, p, (double *) NULL, stats) ; colamd_report (stats) ; if (!ok) { printf ("colamd error!\n") ; exit (1) ; } /* ====================================================================== */ /* print the column ordering */ /* ====================================================================== */ printf ("colamd 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\nsymamd %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 = symamd (B_N, B, q, perm, (double *) NULL, stats, &calloc, &free) ; symamd_report (stats) ; if (!ok) { printf ("symamd error!\n") ; exit (1) ; } /* ====================================================================== */ /* print the symmetric ordering */ /* ====================================================================== */ printf ("symamd 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]) ; exit (0) ; }