nrnmpi.h

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/*
# =============================================================================
# Copyright (c) 2016 - 2021 Blue Brain Project/EPFL
#
# See top-level LICENSE file for details.
# =============================================================================.
*/
 
#pragma once
 
#include <cassert>
#include <string>
#include <type_traits>
#include <vector>
 
#include "coreneuron/mpi/nrnmpiuse.h"
 
#ifndef nrn_spikebuf_size
#define nrn_spikebuf_size 0
#endif
 
namespace coreneuron {
struct NRNMPI_Spikebuf {
    int nspike;
    int gid[nrn_spikebuf_size];
    double spiketime[nrn_spikebuf_size];
};
}  // namespace coreneuron
 
namespace coreneuron {
struct NRNMPI_Spike {
    int gid;
    double spiketime;
};
 
// Those functions and classes are part of a mechanism to dynamically or statically load mpi
// functions
struct mpi_function_base;
 
struct mpi_manager_t {
    void register_function(mpi_function_base* ptr) {
        m_function_ptrs.push_back(ptr);
    }
    void resolve_symbols(void* dlsym_handle);
 
  private:
    std::vector<mpi_function_base*> m_function_ptrs;
    // true when symbols are resolved
};
 
inline mpi_manager_t& mpi_manager() {
    static mpi_manager_t x;
    return x;
}
 
struct mpi_function_base {
    void resolve(void* dlsym_handle);
    operator bool() const {
        return m_fptr;
    }
    mpi_function_base(const char* name)
        : m_name{name} {
        mpi_manager().register_function(this);
    }
 
  protected:
    void* m_fptr{};
    const char* m_name;
};
 
// This could be done with a simpler
//   template <auto fptr> struct function : function_base { ... };
// pattern in C++17...
template <typename>
struct mpi_function {};
 
#define cnrn_make_integral_constant_t(x) std::integral_constant<std::decay_t<decltype(x)>, x>
 
template <typename function_ptr, function_ptr fptr>
struct mpi_function<std::integral_constant<function_ptr, fptr>>: mpi_function_base {
    using mpi_function_base::mpi_function_base;
    template <typename... Args>  // in principle deducible from `function_ptr`
    auto operator()(Args&&... args) const {
#ifdef CORENEURON_ENABLE_MPI_DYNAMIC
        // Dynamic MPI, m_fptr should have been initialised via dlsym.
        assert(m_fptr);
        return (*reinterpret_cast<decltype(fptr)>(m_fptr))(std::forward<Args>(args)...);
#else
        // No dynamic MPI, use `fptr` directly. Will produce link errors if libmpi.so is not linked.
        return (*fptr)(std::forward<Args>(args)...);
#endif
    }
};
}  // namespace coreneuron
#include "coreneuron/mpi/nrnmpidec.h"