halo_exchange.h

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#ifndef HALO_EXCHANGE_H
#define HALO_EXCHANGE_H
 
#include <cstdint>
#include <vector>
 
#include <Kokkos_Core.hpp>
 
#include "comm.h"
#include "common_typedef.h"
#include "distribution.h"
#include "state.h"
 
class HaloExchange {
    public:
        HaloExchange() = default;
        HaloExchange(const Distribution & dist, bool nccl);
 
        void exchange(const State & U) {
            start(U);
            finish(U);
        }
 
        void start(const State & U);
 
        void finish(const State & U);
 
        bool active() const { return !ranks.empty(); }
 
        bool uses_nccl() const { return nccl; }
 
    private:
        void allocate_buffers(uint32_t n_values_per_cell);
 
        std::vector<int> ranks;
        bool nccl = false;
        uint32_t n_values = 0;  // per cell in the buffers: the flow block, then the species
        std::vector<uint32_t> send_offsets, recv_offsets;  // per neighbor, in cells
        Kokkos::View<uint32_t *> send_cells, recv_cells;
        Kokkos::View<rtype *> send_buffer, recv_buffer;
        Kokkos::View<rtype *>::host_mirror_type h_send_buffer, h_recv_buffer;
#ifdef Mallard_HAS_MPI
        std::vector<MPI_Request> requests;
#endif
};
 
#endif // HALO_EXCHANGE_H