AverageState.hpp

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// Copyright (c) 2020 Maikel Nadolski
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// SOFTWARE.
 
#ifndef FUB_AMREX_AVERAGE_STATE_HPP
#define FUB_AMREX_AVERAGE_STATE_HPP
 
#include <AMReX.H>
 
#include "fub/AMReX/ForEachFab.hpp"
#include "fub/AMReX/ViewFArrayBox.hpp"
 
#include "fub/ForEach.hpp"
 
#include <mpi.h>
 
namespace fub::amrex {
 
template <typename InitialValue, typename BinaryOp>
void AccumulateState(const ::amrex::MultiFab& mf, const ::amrex::Box& box,
                     InitialValue&& init, BinaryOp&& binary_op) {
  const auto ncomp = static_cast<std::size_t>(mf.nComp());
  std::vector<double> state_buffer(ncomp);
  span<const double> buffer(state_buffer);
  ForEachFab(mf, [&](const ::amrex::MFIter& mfi) {
    IndexBox<AMREX_SPACEDIM> section =
        AsIndexBox<AMREX_SPACEDIM>(box & mfi.tilebox());
    const ::amrex::FArrayBox& data = mf[mfi];
    ForEachIndex(section, [&](auto... is) {
      ::amrex::IntVect index{static_cast<int>(is)...};
      for (std::size_t comp = 0; comp < ncomp; ++comp) {
        state_buffer[comp] = data(index, static_cast<int>(comp));
      }
      std::invoke(std::forward<BinaryOp>(binary_op),
                  std::forward<InitialValue>(init), buffer);
    });
  });
}
 
template <typename Equation>
void AverageState(Complete<Equation>& state, const ::amrex::MultiFab& mf,
                  const ::amrex::Geometry&, const ::amrex::Box& box) {
  const auto ncomp = static_cast<std::size_t>(mf.nComp());
  std::vector<double> state_buffer(ncomp);
  const std::ptrdiff_t num_cells = box.numPts();
  ForEachFab(execution::seq, mf, [&](const ::amrex::MFIter& mfi) {
    IndexBox<AMREX_SPACEDIM> section =
        AsIndexBox<AMREX_SPACEDIM>(box & mfi.tilebox());
    const ::amrex::FArrayBox& data = mf[mfi];
    for (std::size_t comp = 0; comp < ncomp; ++comp) {
      ForEachIndex(section, [&](auto... is) {
        ::amrex::IntVect index{static_cast<int>(is)...};
        state_buffer[comp] += data(index, static_cast<int>(comp)) /
                              static_cast<double>(num_cells);
      });
    }
  });
  std::vector<double> global_state_buffer(ncomp);
  MPI_Allreduce(state_buffer.data(), global_state_buffer.data(),
                static_cast<int>(ncomp), MPI_DOUBLE, MPI_SUM,
                ::amrex::ParallelDescriptor::Communicator());
  CopyFromBuffer(state, global_state_buffer);
}
 
template <typename Equation>
void AverageState(Conservative<Equation>& state, const ::amrex::MultiFab& mf,
                  const ::amrex::Geometry&, const ::amrex::Box& box) {
  const auto ncomp = static_cast<std::size_t>(mf.nComp());
  std::vector<double> state_buffer(ncomp);
  const std::ptrdiff_t num_cells = box.numPts();
  ForEachFab(mf, [&](const ::amrex::MFIter& mfi) {
    IndexBox<AMREX_SPACEDIM> section =
        AsIndexBox<AMREX_SPACEDIM>(box & mfi.tilebox());
    const ::amrex::FArrayBox& data = mf[mfi];
    for (std::size_t comp = 0; comp < ncomp; ++comp) {
      ForEachIndex(section, [&](auto... is) {
        ::amrex::IntVect index{static_cast<int>(is)...};
        state_buffer[comp] += data(index, static_cast<int>(comp)) /
                              static_cast<double>(num_cells);
      });
    }
  });
  std::vector<double> global_state_buffer(ncomp);
  MPI_Allreduce(state_buffer.data(), global_state_buffer.data(),
                static_cast<int>(ncomp), MPI_DOUBLE, MPI_SUM,
                ::amrex::ParallelDescriptor::Communicator());
  CopyFromBuffer(state, global_state_buffer);
}
 
} // namespace fub::amrex
 
#endif