/*! \file
Copyright (c) 2003, The Regents of the University of California, through
Lawrence Berkeley National Laboratory (subject to receipt of any required
approvals from U.S. Dept. of Energy)

All rights reserved.

The source code is distributed under BSD license, see the file License.txt
at the top-level directory.
*/

/*! @file
 * \brief Get HWPM, heavy-weight perfect matching.
 *
 * <pre>
 * -- Distributed SuperLU routine (version 6.0) --
 * Lawrence Berkeley National Lab, Univ. of California Berkeley.
 * April 2, 2020
 * </pre>
 */

#pragma once
#ifndef dHWPM_CombBLAS_hpp
#define dHWPM_CombBLAS_hpp

#include "CombBLAS/CombBLAS.h"
#include "ApproxWeightPerfectMatching.h"
#include "superlu_ddefs.h"


/*! \brief
 *
 * <pre>
 * Purpose
 * =======
 *   Get perm_r from HWPM, heavy-weight perfect matching, as a
 *   numerical pivoting permutation.
 * 
 * Arguments
 * =========
 *
 * A      (input) SuperMatrix*
 *        The distributed input matrix A of dimension (A->nrow, A->ncol).
 *        A may be overwritten by diag(R)*A*diag(C)*Pc^T.
 *        The type of A can be: Stype = SLU_NR_loc; Dtype = SLU_D; Mtype = SLU_GE.
 *
 * perm   (input) int_t*
 *        Permutation vector describing the transformation performed to
 *        the original matrix A.
 *
 * grid   (input) gridinfo_t*
 *        SuperLU's 2D process mesh.
 *
 * ScalePermstruct (output) dScalePermstruct_t*
 *        ScalePermstruct->perm_r stores the permutation obtained from HWPM.
 *
 * </pre>
 */
void
dGetHWPM(SuperMatrix *A, gridinfo_t *grid, dScalePermstruct_t *ScalePermstruct)
{
    NRformat_loc *Astore;
    int_t  i, irow, fst_row, j, jcol, m, n, m_loc;
    int_t lirow, ljcol;
    int_t  nnz_loc;    /* number of local nonzeros */
    double *nzval_a;
    int    iam, p, procs;
    int_t *perm=nullptr; // placeholder for load balancing permutation for CombBLAS
    procs = grid->nprow * grid->npcol;
    
    if(grid->nprow != grid->npcol)
    {
        printf("HWPM only supports square process grid. Retuning without a permutation.\n");
    }
    combblas::SpParMat < int_t, double, combblas::SpDCCols<int_t,double> > Adcsc(grid->comm);
    std::vector< std::vector < std::tuple<int_t,int_t,double> > > data(procs);
    
    /* ------------------------------------------------------------
     INITIALIZATION.
     ------------------------------------------------------------*/
    iam = grid->iam;
#if ( DEBUGlevel>=1 )
    CHECK_MALLOC(iam, "Enter pdCSR_loc_to_2DBlock()");
#endif
    Astore = (NRformat_loc *) A->Store;
    n = A->ncol;
    m = A->nrow;
    m_loc = Astore->m_loc;
    fst_row = Astore->fst_row;
    
    /* ------------------------------------------------------------
     FIRST PASS OF A:
     COUNT THE NUMBER OF NONZEROS TO BE SENT TO EACH PROCESS,
     THEN ALLOCATE SPACE.
     Re-distribute A from distributed CSR storage to 2D block storage
     conforming CombBLAS API.
     ------------------------------------------------------------*/
    nzval_a = (double *) Astore->nzval;
    nnz_loc = 0;
    for (i = 0; i < m_loc; ++i) {
        for (j = Astore->rowptr[i]; j < Astore->rowptr[i+1]; ++j) {
            if(perm != NULL)
            {
                irow = perm[i+fst_row];         /* Row number in P*A*P^T */
                jcol = perm[Astore->colind[j]]; /* Column number in P*A*P^T */
            }
            else
            {
                irow = i+fst_row;
                jcol = Astore->colind[j];
            }
            p = Adcsc.Owner(m, n , irow, jcol, lirow, ljcol);
            ++ nnz_loc;
            data[p].push_back(std::make_tuple(lirow,ljcol,nzval_a[j]));
            
        }
    }
    
    Adcsc.SparseCommon(data, nnz_loc, m, n, std::plus<double>());
    combblas::FullyDistVec<int_t, int_t> mateRow2Col ( Adcsc.getcommgrid(), m, (int_t) -1);
    combblas::FullyDistVec<int_t, int_t> mateCol2Row ( Adcsc.getcommgrid(), n, (int_t) -1);
    combblas::AWPM(Adcsc, mateRow2Col, mateCol2Row,true);
    
    // now gather the matching vector
    MPI_Comm World = mateRow2Col.getcommgrid()->GetWorld();
    int * rdispls = new int[procs];
    int sendcnt = mateRow2Col.LocArrSize();
    int * recvcnt = new int[procs];
    MPI_Allgather(&sendcnt, 1, MPI_INT, recvcnt, 1, MPI_INT, World);
    rdispls[0] = 0;
    for(int i=0; i<procs-1; ++i)
    {
        rdispls[i+1] = rdispls[i] + recvcnt[i];
    }
    int_t *senddata = (int_t *)mateRow2Col.GetLocArr();
    
    MPI_Allgatherv(senddata, sendcnt, combblas::MPIType<int_t>(), ScalePermstruct->perm_r, recvcnt, rdispls, combblas::MPIType<int_t>(), World);
    
    delete[] rdispls;
    delete[] recvcnt;
    
#if ( DEBUGlevel>=1 )
    CHECK_MALLOC(iam, "Exit dHWPM_CombBLAS()");
#endif
}

#endif /* dHWPM_CombBLAS_hpp */
