Zoltan2_AlgHybridPD2.hpp

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// @HEADER
// *****************************************************************************
//   Zoltan2: A package of combinatorial algorithms for scientific computing
//
// Copyright 2012 NTESS and the Zoltan2 contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef _ZOLTAN2_PDISTANCE2_HPP_
#define _ZOLTAN2_PDISTANCE2_HPP_

#include <vector>
#include <unordered_map>
#include <iostream>
#include <queue>
#ifdef _WIN32
#include <time.h>
#else
#include <sys/time.h>
#endif

#include "Zoltan2_Algorithm.hpp"
#include "Zoltan2_GraphModel.hpp"
#include "Zoltan2_ColoringSolution.hpp"
#include "Zoltan2_Util.hpp"
#include "Zoltan2_TPLTraits.hpp"
#include "Zoltan2_AlltoAll.hpp"


#include "Tpetra_Core.hpp"
#include "Teuchos_RCP.hpp"
#include "Tpetra_Import.hpp"
#include "Tpetra_FEMultiVector.hpp"

#include "Kokkos_Core.hpp"
#include "KokkosSparse_CrsMatrix.hpp"
#include "KokkosKernels_Handle.hpp"
#include "KokkosKernels_IOUtils.hpp"
#include "KokkosGraph_Distance2Color.hpp"
#include "KokkosGraph_Distance2ColorHandle.hpp"



namespace Zoltan2{

template <typename Adapter>
class AlgPartialDistance2 : public AlgTwoGhostLayer<Adapter> {

  public:

    using lno_t = typename Adapter::lno_t;
    using gno_t = typename Adapter::gno_t;
    using offset_t = typename Adapter::offset_t;
    using scalar_t = typename Adapter::scalar_t;
    using base_adapter_t = typename Adapter::base_adapter_t;
    using map_t = Tpetra::Map<lno_t,gno_t>;
    using femv_scalar_t = int;
    using femv_t = Tpetra::FEMultiVector<femv_scalar_t, lno_t, gno_t>;
    using device_type = typename femv_t::device_type;
    using execution_space = typename device_type::execution_space;
    using memory_space = typename device_type::memory_space;
    using host_exec = typename femv_t::host_view_type::device_type::execution_space;
    using host_mem = typename femv_t::host_view_type::device_type::memory_space;

  private:
    //serial and parallel local partial distance-2 coloring function
    template<class ExecutionSpace, typename MemorySpace>
    void localColoring(const size_t nVtx,
           Kokkos::View<lno_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> adjs_view,
           Kokkos::View<offset_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> offset_view,
           Teuchos::RCP<femv_t> femv,
           Kokkos::View<lno_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> vertex_list,
           size_t vertex_list_size = 0,
           bool use_vertex_based_coloring = false){
      using KernelHandle = KokkosKernels::Experimental::KokkosKernelsHandle
        <offset_t, lno_t, lno_t, ExecutionSpace, MemorySpace, MemorySpace>;
      KernelHandle kh;

      //Instead of switching between vertex-based and net-based algorithms,
      //we use only the net-based algorithm, as it is faster than its
      //vertex-based counterpart.
      kh.create_distance2_graph_coloring_handle(KokkosGraph::COLORING_D2_NB_BIT);

      //vertex_list_size indicates whether we have provided a list of vertices to recolor
      //NB_BIT does not currently make use of this.
      if(vertex_list_size != 0){
        kh.get_distance2_graph_coloring_handle()->set_vertex_list(vertex_list, vertex_list_size);
      }

      //the verbose argument should carry through the local coloring
      kh.get_distance2_graph_coloring_handle()->set_verbose(this->verbose);

      //set initial colors to be the colors from femv
      auto femvColors = femv->template getLocalView<Kokkos::Device<ExecutionSpace,MemorySpace> >(Tpetra::Access::ReadWrite);
      auto sv = subview(femvColors,Kokkos::ALL, 0);
      kh.get_distance2_graph_coloring_handle()->set_vertex_colors(sv);

      //call coloring
      KokkosGraph::Experimental::bipartite_color_rows(&kh, nVtx, nVtx, offset_view, adjs_view, true);


      //output total time
      if(this->verbose){
        std::cout<<"\nKokkosKernels Coloring: "
     <<kh.get_distance2_graph_coloring_handle()->get_overall_coloring_time()
     <<"\n";
      }
    }

    //Entry point for parallel local coloring
    virtual void colorInterior(const size_t nVtx,
                       Kokkos::View<lno_t*, device_type> adjs_view,
                       Kokkos::View<offset_t*, device_type> offset_view,
                       Teuchos::RCP<femv_t> femv,
           Kokkos::View<lno_t*, device_type> vertex_list,
           size_t vertex_list_size=0,
                       bool recolor=false){
      this->localColoring<execution_space, memory_space>(nVtx,
                                             adjs_view,
               offset_view,
               femv,
               vertex_list,
               vertex_list_size,
               recolor);
    }
    //Entry point for serial local coloring
    virtual void colorInterior_serial(const size_t nVtx,
                       typename Kokkos::View<lno_t*, device_type >::HostMirror adjs_view,
                       typename Kokkos::View<offset_t*,device_type >::HostMirror offset_view,
                       Teuchos::RCP<femv_t> femv,
                       typename Kokkos::View<lno_t*, device_type>::HostMirror vertex_list,
                       size_t vertex_list_size = 0,
                       bool recolor=false) {
      this->localColoring<host_exec, host_mem>(nVtx,
                                   adjs_view,
                 offset_view,
                 femv,
                 vertex_list,
                 vertex_list_size,
                 recolor);

    }
  public:
    //serial and parallel partial distance-2 conflict detection function
    template <class ExecutionSpace, typename MemorySpace>
    void detectPD2Conflicts(const size_t n_local,
                Kokkos::View<offset_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> dist_offsets,
          Kokkos::View<lno_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> dist_adjs,
          Kokkos::View<int*, Kokkos::Device<ExecutionSpace, MemorySpace>> femv_colors,
          Kokkos::View<lno_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> boundary_verts_view,
          Kokkos::View<lno_t*,
                       Kokkos::Device<ExecutionSpace, MemorySpace> > verts_to_recolor_view,
          Kokkos::View<int*,
                       Kokkos::Device<ExecutionSpace, MemorySpace>,
           Kokkos::MemoryTraits<Kokkos::Atomic> > verts_to_recolor_size_atomic,
          Kokkos::View<lno_t*,
                       Kokkos::Device<ExecutionSpace, MemorySpace> > verts_to_send_view,
          Kokkos::View<size_t*,
                       Kokkos::Device<ExecutionSpace, MemorySpace>,
           Kokkos::MemoryTraits<Kokkos::Atomic> > verts_to_send_size_atomic,
          Kokkos::View<size_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> recoloringSize,
          Kokkos::View<int*, Kokkos::Device<ExecutionSpace, MemorySpace>> rand,
          Kokkos::View<gno_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> gid,
          Kokkos::View<gno_t*, Kokkos::Device<ExecutionSpace, MemorySpace>> ghost_degrees,
          bool recolor_degrees){

      Kokkos::RangePolicy<ExecutionSpace> policy(0,boundary_verts_view.extent(0));
      size_t local_recoloring_size;
      Kokkos::parallel_reduce("PD2 conflict detection",policy, KOKKOS_LAMBDA(const uint64_t& i,size_t& recoloring_size){
    //we only detect conflicts for vertices in the boundary
          const size_t curr_lid = boundary_verts_view(i);
          const int curr_color = femv_colors(curr_lid);
          const size_t vid_d1_adj_begin = dist_offsets(curr_lid);
          const size_t vid_d1_adj_end   = dist_offsets(curr_lid+1);
          const size_t curr_degree = vid_d1_adj_end - vid_d1_adj_begin;
          for(size_t vid_d1_adj = vid_d1_adj_begin; vid_d1_adj < vid_d1_adj_end; vid_d1_adj++){
      //we skip direct distance-1 conflicts, and only resolve distance-2 conflicts.
            size_t vid_d1 = dist_adjs(vid_d1_adj);
            size_t d2_adj_begin = dist_offsets(vid_d1);
            size_t d2_adj_end   = dist_offsets(vid_d1+1);

      //If we find a conflict that uncolors curr_lid, we can safely stop detecting
      //further conflicts starting at curr_lid. Because this is a nested loop,
      //we'll use the found boolean to break twice and move to the next vertex.
            bool found = false;
            for(size_t vid_d2_adj = d2_adj_begin; vid_d2_adj < d2_adj_end; vid_d2_adj++){
              const size_t vid_d2 = dist_adjs(vid_d2_adj);
              size_t vid_d2_degree = 0;

        //calculate the degree for degree-based recoloring
              if(vid_d2 < n_local){
                vid_d2_degree = dist_offsets(vid_d2+1) - dist_offsets(vid_d2);
              } else {
                vid_d2_degree = ghost_degrees(vid_d2-n_local);
              }
        //resolve conflict
              if(curr_lid != vid_d2 && femv_colors(vid_d2) == curr_color){
                if(curr_degree < vid_d2_degree && recolor_degrees){
                  found = true;
                  femv_colors(curr_lid) = 0;
                  recoloring_size++;
                  break;//---------------------------------------------------
                } else if(vid_d2_degree < curr_degree && recolor_degrees){//|
                  femv_colors(vid_d2) = 0;                                //|
                  recoloring_size++;                                      //|
                } else if(rand(curr_lid) < rand(vid_d2)){                 //|
                  found = true;                                           //|
                  femv_colors(curr_lid) = 0;                              //|
                  recoloring_size++;                                      //|
                  break;//--------------------------------------------------|
                } else if(rand(vid_d2) < rand(curr_lid)){                 //|
                  femv_colors(vid_d2) = 0;                                //|
                  recoloring_size++;                                      //|
                } else {                                                  //|
                  if(gid(curr_lid) >= gid(vid_d2)){                       //|
                    found = true;                                         //|
                    femv_colors(curr_lid) = 0;                            //|
                    recoloring_size++;                                    //|
                    break;//------------------------------------------------|
                  } else {                                                //|
                    femv_colors(vid_d2) = 0;                              //|
                    recoloring_size++;//                                    v
                  }//              If we uncolor the vertex whose neighbors we're
                }  //              checking, each subsequent conflict check will
              }    //              not do anything productive. We need this------
            }      //              to completely move on to the next vertex.    |
            if(found) break;//<--------------------------------------------------
          }
        },local_recoloring_size);
      Kokkos::deep_copy(recoloringSize, local_recoloring_size);
        Kokkos::fence();
  //update the verts_to_send and verts_to_recolor views
        Kokkos::parallel_for("rebuild verts_to_send and verts_to_recolor",
           Kokkos::RangePolicy<ExecutionSpace>(0,femv_colors.size()),
           KOKKOS_LAMBDA(const uint64_t& i){
          if(femv_colors(i) == 0){
            if(i < n_local){
        //we only send vertices owned by the current process
              verts_to_send_view(verts_to_send_size_atomic(0)++) = i;
            }
      //we need to recolor all vertices for consistency.
            verts_to_recolor_view(verts_to_recolor_size_atomic(0)++) = i;
          }
        });
        Kokkos::fence();

    }
    //Entry point for parallel conflict detection
    virtual void detectConflicts(const size_t n_local,
                                 Kokkos::View<offset_t*, device_type > dist_offsets_dev,
                                 Kokkos::View<lno_t*, device_type > dist_adjs_dev,
                                 Kokkos::View<int*,device_type > femv_colors,
                                 Kokkos::View<lno_t*, device_type > boundary_verts_view,
                                 Kokkos::View<lno_t*,
                                              device_type > verts_to_recolor_view,
                                 Kokkos::View<int*,
                                              device_type,
                                              Kokkos::MemoryTraits<Kokkos::Atomic>> verts_to_recolor_size_atomic,
                                 Kokkos::View<lno_t*,
                                              device_type > verts_to_send_view,
                                 Kokkos::View<size_t*,
                                              device_type,
                                              Kokkos::MemoryTraits<Kokkos::Atomic>> verts_to_send_size_atomic,
                                 Kokkos::View<size_t*, device_type> recoloringSize,
                                 Kokkos::View<int*,
                                              device_type> rand,
                                 Kokkos::View<gno_t*,
                                              device_type> gid,
                                 Kokkos::View<gno_t*,
                                              device_type> ghost_degrees,
                                 bool recolor_degrees){

      this->detectPD2Conflicts<execution_space, memory_space>(n_local,
                                                  dist_offsets_dev,
                    dist_adjs_dev,
                    femv_colors,
                    boundary_verts_view,
                    verts_to_recolor_view,
                    verts_to_recolor_size_atomic,
                    verts_to_send_view,
                    verts_to_send_size_atomic,
                    recoloringSize,
                    rand,
                    gid,
                    ghost_degrees,
                    recolor_degrees);
    }
    //Entry point for serial conflict detection
    virtual void detectConflicts_serial(const size_t n_local,
                                 typename Kokkos::View<offset_t*, device_type >::HostMirror dist_offsets_host,
                                 typename Kokkos::View<lno_t*, device_type >::HostMirror dist_adjs_host,
                                 typename Kokkos::View<int*,device_type >::HostMirror femv_colors,
                                 typename Kokkos::View<lno_t*, device_type >::HostMirror boundary_verts_view,
                                 typename Kokkos::View<lno_t*,device_type>::HostMirror verts_to_recolor,
                                 typename Kokkos::View<int*,device_type>::HostMirror verts_to_recolor_size,
                                 typename Kokkos::View<lno_t*,device_type>::HostMirror verts_to_send,
                                 typename Kokkos::View<size_t*,device_type>::HostMirror verts_to_send_size,
                                 typename Kokkos::View<size_t*, device_type>::HostMirror recoloringSize,
                                 typename Kokkos::View<int*,  device_type>::HostMirror rand,
                                 typename Kokkos::View<gno_t*,device_type>::HostMirror gid,
                                 typename Kokkos::View<gno_t*,device_type>::HostMirror ghost_degrees,
                                 bool recolor_degrees) {

      this->detectPD2Conflicts<host_exec, host_mem>(n_local,
                                        dist_offsets_host,
                      dist_adjs_host,
                      femv_colors,
                      boundary_verts_view,
                      verts_to_recolor,
                      verts_to_recolor_size,
                      verts_to_send,
                      verts_to_send_size,
                      recoloringSize,
                      rand,
                      gid,
                      ghost_degrees,
                      recolor_degrees);
    }
    //Entry point for boundary construction
    virtual void constructBoundary(const size_t n_local,
                                   Kokkos::View<offset_t*, device_type> dist_offsets_dev,
                                   Kokkos::View<lno_t*, device_type> dist_adjs_dev,
                                   typename Kokkos::View<offset_t*, device_type>::HostMirror dist_offsets_host,
                                   typename Kokkos::View<lno_t*, device_type>::HostMirror dist_adjs_host,
                                   Kokkos::View<lno_t*, device_type>& boundary_verts,
                                   Kokkos::View<lno_t*,
                                                device_type > verts_to_send_view,
                                   Kokkos::View<size_t*,
                                                device_type,
                                                Kokkos::MemoryTraits<Kokkos::Atomic>> verts_to_send_size_atomic){
      //count the number of boundary vertices to correctly allocate
      //the boundary vertex view on device
      gno_t boundary_size_temp = 0;
      for(size_t i = 0; i < n_local; i++){
        for(offset_t j = dist_offsets_host(i); j < dist_offsets_host(i+1); j++){
          if((size_t)dist_adjs_host(j) >= n_local){
            boundary_size_temp++;
            break;
          }
          bool found = false;
          for(offset_t k = dist_offsets_host(dist_adjs_host(j)); k < dist_offsets_host(dist_adjs_host(j)+1); k++){
            if((size_t)dist_adjs_host(k) >= n_local){
              boundary_size_temp++;
              found = true;
              break;
            }
          }
          if(found) break;
        }
      }

      //Initialize the boundary on host
      boundary_verts = Kokkos::View<lno_t*, device_type>("boundary verts",boundary_size_temp);
      typename Kokkos::View<lno_t*, device_type>::HostMirror boundary_verts_host = Kokkos::create_mirror_view(boundary_verts);

      //reset the boundary size count to use as an index to construct the view
      boundary_size_temp = 0;

      for(size_t i = 0; i < n_local; i++){
        for(offset_t j = dist_offsets_host(i); j < dist_offsets_host(i+1); j++){
          if((size_t)dist_adjs_host(j) >= n_local){
            boundary_verts_host(boundary_size_temp++) = i;
            break;
          }
          bool found = false;
          for(offset_t k = dist_offsets_host(dist_adjs_host(j)); k < dist_offsets_host(dist_adjs_host(j)+1); k++){
            if((size_t)dist_adjs_host(k) >= n_local){
              boundary_verts_host(boundary_size_temp++) = i;
              found = true;
              break;
            }
          }
          if(found) break;
        }
      }
      //copy boundary over to device views
      Kokkos::deep_copy(boundary_verts, boundary_verts_host);

      //initialize the verts_to_send views
      Kokkos::parallel_for("init verts to send",
       Kokkos::RangePolicy<execution_space, int>(0,n_local),
       KOKKOS_LAMBDA(const int& i){
       for(offset_t j = dist_offsets_dev(i); j < dist_offsets_dev(i+1); j++){
        if((size_t)dist_adjs_dev(j) >= n_local){
          verts_to_send_view(verts_to_send_size_atomic(0)++) = i;
          break;
        }
        bool found = false;
        for(offset_t k = dist_offsets_dev(dist_adjs_dev(j)); k < dist_offsets_dev(dist_adjs_dev(j)+1); k++){
          if((size_t)dist_adjs_dev(k) >= n_local){
            verts_to_send_view(verts_to_send_size_atomic(0)++) = i;
            found = true;
            break;
          }
        }
        if(found) break;
       }
      });
      Kokkos::fence();

    }


  public:
    AlgPartialDistance2(
      const RCP<const base_adapter_t> &adapter_,
      const RCP<Teuchos::ParameterList> &pl_,
      const RCP<Environment> &env_,
      const RCP<const Teuchos::Comm<int> > &comm_)
    : AlgTwoGhostLayer<Adapter>(adapter_,pl_,env_,comm_){}



}; //end class



}//end namespace Zoltan2

#endif