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//------------------------------------------------------------------------------
// CHOLMOD/MATLAB/bisect: MATLAB interface to CHOLMOD graph bisection
//------------------------------------------------------------------------------
// CHOLMOD/MATLAB Module. Copyright (C) 2005-2023, Timothy A. Davis.
// All Rights Reserved.
// SPDX-License-Identifier: GPL-2.0+
//------------------------------------------------------------------------------
// MATLAB(tm) is a Trademark of The MathWorks, Inc.
// METIS is Copyrighted by G. Karypis
// Find an node separator of an undirected graph, using
// METIS_ComputeVertexSeparator.
//
// Usage:
//
// s = bisect (A) bisects A, uses tril(A)
// s = bisect (A, 'sym') bisects A, uses tril(A)
// s = bisect (A, 'row') bisects A*A'
// s = bisect (A, 'col') bisects A'*A
//
// Node i of the graph is in the left graph if s(i)=0, the right graph if
// s(i)=1, and in the separator if s(i)=2.
//
// Requirse METIS and the CHOLMOD Partition Module.
#include "sputil2.h"
void mexFunction
(
int nargout,
mxArray *pargout [ ],
int nargin,
const mxArray *pargin [ ]
)
{
#ifndef NPARTITION
double dummy = 0 ;
int64_t *Partition ;
cholmod_sparse *A, Amatrix, *C ;
cholmod_common Common, *cm ;
int64_t n, transpose, c ;
char buf [LEN] ;
//--------------------------------------------------------------------------
// start CHOLMOD and set defaults
//--------------------------------------------------------------------------
cm = &Common ;
cholmod_l_start (cm) ;
sputil2_config (SPUMONI, cm) ;
//--------------------------------------------------------------------------
// get inputs
//--------------------------------------------------------------------------
if (nargout > 1 || nargin < 1 || nargin > 2)
{
mexErrMsgTxt ("Usage: p = bisect (A, mode)") ;
}
//--------------------------------------------------------------------------
// get input matrix A
//--------------------------------------------------------------------------
A = sputil2_get_sparse_pattern (pargin [0], CHOLMOD_DOUBLE, &Amatrix, cm) ;
//--------------------------------------------------------------------------
// get A->stype, default is to use tril(A)
//--------------------------------------------------------------------------
A->stype = -1 ;
transpose = FALSE ;
if (nargin > 1)
{
buf [0] = '\0' ;
if (mxIsChar (pargin [1]))
{
mxGetString (pargin [1], buf, LEN) ;
}
c = buf [0];
if (tolower (c) == 'r')
{
// unsymmetric case (A*A') if string starts with 'r'
transpose = FALSE ;
A->stype = 0 ;
}
else if (tolower (c) == 'c')
{
// unsymmetric case (A'*A) if string starts with 'c'
transpose = TRUE ;
A->stype = 0 ;
}
else if (tolower (c) == 's')
{
// symmetric case (A) if string starts with 's'
transpose = FALSE ;
A->stype = -1 ;
}
else
{
mexErrMsgTxt ("bisect: p=bisect(A,mode) ; unrecognized mode") ;
}
}
if (A->stype && A->nrow != A->ncol)
{
mexErrMsgTxt ("bisect: A must be square") ;
}
//--------------------------------------------------------------------------
// bisect with CHOLMOD's interface to METIS_ComputeVertexSeparator
//--------------------------------------------------------------------------
bool ok ;
if (transpose)
{
// C = A', and then bisect C*C'
cholmod_sparse *C = cholmod_l_transpose (A, 0, cm) ;
n = C->nrow ;
Partition = cholmod_l_malloc (n, sizeof (int64_t), cm) ;
ok = (cholmod_l_bisect (C, NULL, 0, TRUE, Partition, cm) >= 0) ;
cholmod_l_free_sparse (&C, cm) ;
}
else
{
// biset A or A*A'
n = A->nrow ;
Partition = cholmod_l_malloc (n, sizeof (int64_t), cm) ;
ok = (cholmod_l_bisect (A, NULL, 0, TRUE, Partition, cm) >= 0) ;
}
//--------------------------------------------------------------------------
// return results and free workspace
//--------------------------------------------------------------------------
sputil2_free_sparse (&A, &Amatrix, 0, cm) ;
if (!ok) mexErrMsgTxt ("bisect failed") ;
pargout [0] = sputil2_put_int (Partition, n, 0) ;
cholmod_l_free (n, sizeof (int64_t), Partition, cm) ;
cholmod_l_finish (cm) ;
if (SPUMONI > 0) cholmod_l_print_common (" ", cm) ;
#else
mexErrMsgTxt ("METIS and the CHOLMOD Partition Module not installed\n") ;
#endif
}
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