graph_compute_projection.c

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/**
 *
 * @file graph_compute_projection.c
 *
 * PaStiX graph routine to compute projection of lower levels supernodes
 *
 * @copyright 2004-2025 Bordeaux INP, CNRS (LaBRI UMR 5800), Inria,
 *                      Univ. Bordeaux. All rights reserved.
 *
 * @version 6.4.0
 * @author Gregoire Pichon
 * @author Pierre Ramet
 * @author Mathieu Faverge
 * @author Tony Delarue
 * @date 2024-07-05
 *
 **/
#include "common.h"
#include "pastix/order.h"
#include "blend/extendVector.h"
#include "graph/graph.h"
 
/**
 *******************************************************************************
 *
 * @brief TODO
 *
 *******************************************************************************
 *
 * @param[in] graph
 *          TODO
 *
 * @param[in] vertlvl
 *          TODO
 *
 * @param[in] order
 *          TODO
 *
 * @param[in] subgraph
 *          TODO
 *
 * @param[in] suborder
 *          TODO
 *
 * @param[in] fnode
 *          TODO
 *
 * @param[in] lnode
 *          TODO
 *
 * @param[in] sn_level
 *          TODO
 *
 * @param[in] distance
 *          TODO
 *
 * @param[in] maxdepth
 *          TODO
 *
 * @param[in] maxwidth
 *          TODO
 *
 * @param[in] depthsze
 *          TODO
 *
 *******************************************************************************/
void
graphComputeProjection( const pastix_graph_t *graph,
                        const int            *vertlvl,
                        pastix_order_t       *order,
                        const pastix_graph_t *subgraph,
                        pastix_order_t       *suborder,
                        pastix_int_t          fnode,
                        pastix_int_t          lnode,
                        pastix_int_t          sn_level,
                        pastix_int_t          distance,
                        pastix_int_t          maxdepth,
                        pastix_int_t          maxwidth,
                        pastix_int_t         *depthsze )
{
    ExtendVectorINT vec;
    pastix_int_t baseval = graph->colptr[0];
    pastix_int_t n, i, ip, j, jp, jj, d, k, sze;
    pastix_int_t lvl, depth;
    const pastix_int_t *colptr;
    const pastix_int_t *rows;
    pastix_int_t *peritab, *subvertlvl, *subvert;
    pastix_int_t *perm, *invp;
 
    n = lnode - fnode;
    MALLOC_INTERN( subvertlvl, n, pastix_int_t );
    extendint_Init( &vec, (sqrt(n)+1) * pastix_imax( distance, maxwidth ) * 2 );
 
    /* (i, j ) in initial ordering  */
    /* (ip,jp) in permuted ordering */
    colptr  = graph->colptr;
    rows    = graph->rowptr;
    peritab = order->peritab;
    subvert = subvertlvl;
 
    for (ip=fnode; ip<lnode; ip++, subvert++) {
        extendint_Clear( &vec );
 
        /* i^th vertex in the initial numbering */
        extendint_Add( &vec, peritab[ip] );
        *subvert = -maxdepth-1;
        sze =  1;
        d   = -1;
        k   =  0;
 
        while( d < distance ) {
            for(; k<sze; k++) {
                i = extendint_Read( &vec, k );
 
                for (jj = colptr[i  ]-baseval;
                     jj < colptr[i+1]-baseval; jj++) {
 
                    j   = rows[jj]-baseval;
                    lvl = vertlvl[j];
 
                    /*
                     * If lvl is equal to sn_level, the node belong to the same supernode,
                     * and if lvl is lower than sn_level, then the node belongs to a
                     * supernode higher in the elimination tree.
                     * In both cases, we avoid to connect to a supernode through them.
                     */
                    if ( lvl <= sn_level ) {
                        continue;
                    }
 
                    /*
                     * Store the negative depth to sort in ascending order with
                     * nodes connected to deeper levels first
                     */
                    depth = sn_level - lvl;
                    *subvert = pastix_imax( depth, *subvert );
 
                    extendint_Add( &vec, j );
                }
            }
            d++;
            sze = extendint_Size( &vec );
        }
    }
 
    perm = suborder->permtab;
    invp = suborder->peritab;
 
    /*
     * Enlarge the projections
     */
    if ( maxwidth > 0 ) {
        pastix_int_t *subvertlv2;
        void *sortptr[3];
 
        sortptr[0] = subvertlvl;
        sortptr[1] = invp;
        sortptr[2] = order->peritab + fnode;
 
        qsort3IntAsc( sortptr, n );
 
        /* Generate the new perm array for the subgraph */
        for(i=0; i<n; i++) {
            j = invp[i];
            assert( (j >= 0) && (j < n) );
            perm[j] = i;
        }
 
        MALLOC_INTERN( subvertlv2, n, pastix_int_t );
        memcpy( subvertlv2, subvertlvl, n * sizeof(pastix_int_t) );
 
        colptr = subgraph->colptr;
        rows   = subgraph->rowptr;
        maxdepth = -maxdepth;
 
        /*
         * We do the loop in reverse order to first enlarge the nodes connected
         * to the highest supernodes.
         */
        for (ip=n-1; ip>=0; ip--) {
            if ( subvertlv2[ip] < maxdepth ) {
                break;
            }
 
            extendint_Clear( &vec );
            /* i^th vertex in the initial numbering */
            extendint_Add( &vec, invp[ip] );
            sze =  1;
            d   =  0;
            k   =  0;
 
            while( d < maxwidth ) {
                for(; k<sze; k++) {
                    i = extendint_Read( &vec, k );
                    assert( subvertlvl[ip] == subvertlvl[ perm[i] ] );
 
                    for (jj = colptr[i  ];
                         jj < colptr[i+1]; jj++) {
 
                        j  = rows[jj];
                        jp = perm[j];
 
                        /* If j has already been seen because connected to an higher sn_level */
                        if ( subvertlv2[jp] > subvertlv2[ip] ) {
                            continue;
                        }
                        subvertlvl[jp] = subvertlvl[ip];
                        extendint_Add( &vec, j );
                    }
                }
                d++;
                sze = extendint_Size( &vec );
            }
        }
        maxdepth = -maxdepth;
 
        memFree_null( subvertlv2 );
    }
 
    /* Sort again the peritab array associated to the subgraph */
    {
        void *sortptr[3];
        sortptr[0] = subvertlvl;
        sortptr[1] = invp;
        sortptr[2] = order->peritab + fnode;
 
        qsort3IntAsc( sortptr, n );
 
        /* Update the perm array */
        for(i=0; i<n; i++) {
            perm[invp[i]] = i;
        }
    }
 
    /* Compute the sizes of each depth */
    memset( depthsze, 0, maxdepth * sizeof(pastix_int_t) );
    {
        int d = 0;
        for(i=n-1; i >= 0; i--) {
            while ( subvertlvl[i] < (-d-1) ) {
                d++;
            }
            if ( d >= maxdepth ) {
                break;
            }
            depthsze[d] ++;
        }
    }
 
    extendint_Exit( &vec );
    free(subvertlvl);
}