//------------------------------------------------------------------------------
// CHOLMOD/Cholesky/cholmod_colamd: COLAMD interface for CHOLMOD
//------------------------------------------------------------------------------

// CHOLMOD/Cholesky Module.  Copyright (C) 2005-2022, Timothy A. Davis
// All Rights Reserved.
// SPDX-License-Identifier: LGPL-2.1+

//------------------------------------------------------------------------------

/* CHOLMOD interface to the COLAMD ordering routine (version 2.4 or later).
 * Finds a permutation p such that the Cholesky factorization of PAA'P' is
 * sparser than AA' using colamd.  If the postorder input parameter is TRUE,
 * the column etree is found and postordered, and the colamd ordering is then
 * combined with its postordering.  A must be unsymmetric.
 *
 * There can be no duplicate entries in f.
 * f can be length 0 to n if A is m-by-n.
 *
 * workspace: Iwork (4*nrow+ncol), Head (nrow+1), Flag (nrow)
 *	Allocates a copy of its input matrix, which
 *	is then used as CCOLAMD's workspace.
 *
 * Supports any xtype (pattern, real, complex, or zomplex)
 */

#include "cholmod_internal.h"

#ifndef NCHOLESKY

#include "colamd.h"
#if (!defined (COLAMD_VERSION) || (COLAMD_VERSION < COLAMD_VERSION_CODE (2,5)))
#error "COLAMD v2.5 or later is required"
#endif

/* ========================================================================== */
/* === cholmod_colamd ======================================================= */
/* ========================================================================== */

int CHOLMOD(colamd)
(
    /* ---- input ---- */
    cholmod_sparse *A,	/* matrix to order */
    Int *fset,		/* subset of 0:(A->ncol)-1 */
    size_t fsize,	/* size of fset */
    int postorder,	/* if TRUE, follow with a coletree postorder */
    /* ---- output --- */
    Int *Perm,		/* size A->nrow, output permutation */
    /* --------------- */
    cholmod_common *Common
)
{
    double knobs [COLAMD_KNOBS] ;
    cholmod_sparse *C ;
    Int *NewPerm, *Parent, *Post, *Work2n ;
    Int k, nrow, ncol ;
    size_t s, alen ;
    int ok = TRUE ;

    /* ---------------------------------------------------------------------- */
    /* check inputs */
    /* ---------------------------------------------------------------------- */

    RETURN_IF_NULL_COMMON (FALSE) ;
    RETURN_IF_NULL (A, FALSE) ;
    RETURN_IF_NULL (Perm, FALSE) ;
    RETURN_IF_XTYPE_INVALID (A, CHOLMOD_PATTERN, CHOLMOD_ZOMPLEX, FALSE) ;
    if (A->stype != 0)
    {
	ERROR (CHOLMOD_INVALID, "matrix must be unsymmetric") ;
	return (FALSE) ;
    }
    Common->status = CHOLMOD_OK ;

    /* ---------------------------------------------------------------------- */
    /* get inputs */
    /* ---------------------------------------------------------------------- */

    nrow = A->nrow ;
    ncol = A->ncol ;

    /* ---------------------------------------------------------------------- */
    /* allocate workspace */
    /* ---------------------------------------------------------------------- */

    /* Note: this is less than the space used in cholmod_analyze, so if
     * cholmod_colamd is being called by that routine, no space will be
     * allocated.
     */

    /* s = 4*nrow + ncol */
    s = CHOLMOD(mult_size_t) (nrow, 4, &ok) ;
    s = CHOLMOD(add_size_t) (s, ncol, &ok) ;

#if ( ITYPE == CHOLMOD_LONG )
    alen = colamd_l_recommended (A->nzmax, ncol, nrow) ;
    colamd_l_set_defaults (knobs) ;
#else
    alen = colamd_recommended (A->nzmax, ncol, nrow) ;
    colamd_set_defaults (knobs) ;
#endif

    if (!ok || alen == 0)
    {
	ERROR (CHOLMOD_TOO_LARGE, "matrix invalid or too large") ;
	return (FALSE) ;
    }

    CHOLMOD(allocate_work) (0, s, 0, Common) ;
    if (Common->status < CHOLMOD_OK)
    {
	return (FALSE) ;
    }

    /* ---------------------------------------------------------------------- */
    /* allocate COLAMD workspace */
    /* ---------------------------------------------------------------------- */

    C = CHOLMOD(allocate_sparse) (ncol, nrow, alen, TRUE, TRUE, 0,
	    CHOLMOD_PATTERN, Common) ;

    /* ---------------------------------------------------------------------- */
    /* copy (and transpose) the input matrix A into the colamd workspace */
    /* ---------------------------------------------------------------------- */

    /* C = A (:,f)', which also packs A if needed. */
    /* workspace: Iwork (nrow if no fset; MAX (nrow,ncol) if fset) */
    ok = CHOLMOD(transpose_unsym) (A, 0, NULL, fset, fsize, C, Common) ;

    /* ---------------------------------------------------------------------- */
    /* order the matrix (destroys the contents of C->i and C->p) */
    /* ---------------------------------------------------------------------- */

    /* get parameters */
    if (Common->current < 0 || Common->current >= CHOLMOD_MAXMETHODS)
    {
	/* this is the CHOLMOD default, not the COLAMD default */
	knobs [COLAMD_DENSE_ROW] = -1 ;
    }
    else
    {
	/* get the knobs from the Common parameters */
	knobs [COLAMD_DENSE_COL] = Common->method[Common->current].prune_dense ;
	knobs [COLAMD_DENSE_ROW] = Common->method[Common->current].prune_dense2;
	knobs [COLAMD_AGGRESSIVE] = Common->method[Common->current].aggressive ;
    }

    if (ok)
    {
	Int *Cp ;
	Int stats [COLAMD_STATS] ;
	Cp = C->p ;

#if ( ITYPE == CHOLMOD_LONG )
	colamd_l (ncol, nrow, alen, C->i, Cp, knobs, stats) ;
#else
	colamd (ncol, nrow, alen, C->i, Cp, knobs, stats) ;
#endif

	ok = stats [COLAMD_STATUS] ;
	ok = (ok == COLAMD_OK || ok == COLAMD_OK_BUT_JUMBLED) ;
	/* permutation returned in C->p, if the ordering succeeded */
	for (k = 0 ; k < nrow ; k++)
	{
	    Perm [k] = Cp [k] ;
	}
    }

    CHOLMOD(free_sparse) (&C, Common) ;

    /* ---------------------------------------------------------------------- */
    /* column etree postordering */
    /* ---------------------------------------------------------------------- */

    if (postorder)
    {
	/* use the last 2*n space in Iwork for Parent and Post */
	Work2n = Common->Iwork ;
	Work2n += 2*((size_t) nrow) + ncol ;
	Parent = Work2n ;		/* size nrow (i/i/l) */
	Post   = Work2n + nrow ;	/* size nrow (i/i/l) */

	/* workspace: Iwork (2*nrow+ncol), Flag (nrow), Head (nrow+1) */
	ok = ok && CHOLMOD(analyze_ordering) (A, CHOLMOD_COLAMD, Perm, fset,
		fsize, Parent, Post, NULL, NULL, NULL, Common) ;

	/* combine the colamd permutation with its postordering */
	if (ok)
	{
	    NewPerm = Common->Iwork ;		/* size nrow (i/i/l) */
	    for (k = 0 ; k < nrow ; k++)
	    {
		NewPerm [k] = Perm [Post [k]] ;
	    }
	    for (k = 0 ; k < nrow ; k++)
	    {
		Perm [k] = NewPerm [k] ;
	    }
	}
    }

    return (ok) ;
}
#endif
