如何通过 Boost.MPI 发送 2d Boost.MultiArray 的子数组？

Question

我需要发送对 Boost.MultiArray 和 Boost.MPI 的二维子数组的引用。现在我有以下代码：

matrix_type::array_view<2>::type
                    current_process_batch = matrix[boost::indices[range(bias, finish_line)][range(0, width)]];
world.send(rank, BEGIN_TAG, current_process_batch);

但我在尝试执行它时也遇到以下错误:

/usr/local/include/boost/serialization/access.hpp:116:11: error: no member named 'serialize' in 'boost::detail::multi_array::multi_array_view<double, 2>'
        t.serialize(ar, file_version);

谁能帮我把它发送到另一个进程？

Answer 1

您需要实现序列化。

这是一个通用的 multi_array<T. Dims> 序列化程序：

namespace boost::serialization {
    template <typename Ar, typename T, size_t Dims>
        void save(Ar& ar, boost::multi_array<T, Dims> const& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            std::copy_n(ma.shape(), Dims, shape.begin());
            ar & make_nvp("shape", shape)
               & make_nvp("data", make_array(ma.data(), ma.num_elements()));
        }

    template <typename Ar, typename T, size_t Dims>
        void load(Ar& ar, boost::multi_array<T, Dims>& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            ar & make_nvp("shape", shape);

            ma.resize(shape);
            ar & make_nvp("data", make_array(const_cast<T*>(ma.data()), ma.num_elements()));
        }

    template <typename Ar, typename T, size_t Dims>
        void serialize(Ar& ar, boost::multi_array<T, Dims>& ma, unsigned version) {
            split_free(ar, ma, version);
        }
}

看到了Live On Coliru

auto make_multi_array() {
    boost::multi_array<int, 2> ma(boost::extents[7][4]);
    std::iota(ma.data(), ma.data() + ma.num_elements(), 10);
    return ma;
}

int main() {
    auto const original = make_multi_array();

    {
        std::ofstream os("array.txt");
        boost::archive::text_oarchive oa(os);

        oa << original;
    }

    std::cout << std::ifstream("array.txt").rdbuf() << "\n";

    {
        std::ifstream is("array.txt");
        boost::archive::text_iarchive ia(is);

        boost::multi_array<int, 2> restored;
        ia >> restored;

        assert(restored == original);
    }
}

版画

22 serialization::archive 17 0 0 0 0 2 7 4 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

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嗯。已经接受了吗？很晚才注意到我实际上并没有很好地阅读您的问题。你想序列化一个视图。你不能，真的。你不能"deserialize a view"。

您最多可以做的是反序列化成一个视图。

Note also that

serializing the whole array could be (much) more efficient if the size difference isn't huge

the view types are not public interface for the library, i.e. it may break in future versions of Boost. If in doubt, serialize the arrays themselves

这里还有一些机器：

添加对 detail::multi_array::multi_array_view<...> 的支持，因为它可以反序列化 INTO 仅匹配形状的现有视图
添加对 detail::multi_array::const_multi_array_view<...> 的支持，仅用于序列化。由于显而易见的原因，所述视图只能反序列化为非常量视图。
用子视图扩展演示，在序列化后对初始数组进行补丁，因此我们可以验证将补丁读入恢复数组的等效视图与原始数组具有相同的效果（在检查补丁创建了预期的不匹配后 20 != 999）。

Live On Coliru

#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/array.hpp>
#include <boost/serialization/nvp.hpp>
#include <boost/serialization/array_wrapper.hpp>
#include <boost/multi_array.hpp>
#include <iostream>
#include <fstream>

namespace boost::serialization {
    template <typename Ar, typename T, size_t Dims>
        void save(Ar& ar, boost::detail::multi_array::const_multi_array_view<T, Dims> const& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            std::copy_n(ma.shape(), Dims, shape.begin());
            ar & make_nvp("shape", shape);

            for (auto i = 0; i < shape[0]; ++i) {
                for (auto j = 0; j < shape[1]; ++j) {
                    ar & make_nvp("item", ma[i][j]);
                }
            }
        }

    template <typename Ar, typename T, size_t Dims>
        void load(Ar&, boost::detail::multi_array::const_multi_array_view<T, Dims>&, unsigned) {
            static_assert(not Ar::is_loading::value, "const_multi_array_view immutable");
        }

    template <typename Ar, typename T, size_t Dims>
        void serialize(Ar& ar, boost::detail::multi_array::const_multi_array_view<T, Dims>& ma, unsigned version) {
            split_free(ar, ma, version);
        }

    template <typename Ar, typename T, size_t Dims>
        void save(Ar& ar, boost::detail::multi_array::multi_array_view<T, Dims> const& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            std::copy_n(ma.shape(), Dims, shape.begin());
            ar & make_nvp("shape", shape);

            for (auto i = 0; i < shape[0]; ++i) {
                for (auto j = 0; j < shape[1]; ++j) {
                    ar & make_nvp("item", ma[i][j]);
                }
            }
        }

    template <typename Ar, typename T, size_t Dims>
        void load(Ar& ar, boost::detail::multi_array::multi_array_view<T, Dims>& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            ar & make_nvp("shape", shape);

            if (!std::equal(begin(shape), end(shape), ma.shape()))
                throw std::logic_error("multi_array_view shape mismatch");

            for (auto i = 0; i < shape[0]; ++i) {
                for (auto j = 0; j < shape[1]; ++j) {
                    ar & make_nvp("item", ma[i][j]);
                }
            }
        }

    template <typename Ar, typename T, size_t Dims>
        void serialize(Ar& ar, boost::detail::multi_array::multi_array_view<T, Dims>& ma, unsigned version) {
            split_free(ar, ma, version);
        }

    template <typename Ar, typename T, size_t Dims>
        void save(Ar& ar, boost::multi_array<T, Dims> const& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            std::copy_n(ma.shape(), Dims, shape.begin());
            ar & make_nvp("shape", shape)
               & make_nvp("data", make_array(ma.data(), ma.num_elements()));
        }

    template <typename Ar, typename T, size_t Dims>
        void load(Ar& ar, boost::multi_array<T, Dims>& ma, unsigned /*version*/) {
            std::array<int, Dims> shape;
            ar & make_nvp("shape", shape);

            ma.resize(shape);
            ar & make_nvp("data", make_array(const_cast<T*>(ma.data()), ma.num_elements()));
        }

    template <typename Ar, typename T, size_t Dims>
        void serialize(Ar& ar, boost::multi_array<T, Dims>& ma, unsigned version) {
            split_free(ar, ma, version);
        }
}

auto make_multi_array() {
    boost::multi_array<int, 2> ma(boost::extents[7][4]);
    std::iota(ma.data(), ma.data() + ma.num_elements(), 10);
    return ma;
}

int main() {
    using range = boost::multi_array_types::index_range;
    auto original = make_multi_array();
    auto const SLICE = boost::indices[range(1,3)][range(1,3)];

    {
        std::ofstream os("array.txt");
        boost::archive::text_oarchive oa(os);

        // only serialize initial array:
        oa << original;

        // modify through a sub-view
        auto sub = original[SLICE];
        original[2][2] = 999;

        // serialize the patch
        oa << sub;

        auto const& const_original = original;
        auto const_sub = const_original[SLICE];
        oa << const_sub; // compiles
    }

    std::cout << std::ifstream("array.txt").rdbuf() << "\n";

    {
        std::ifstream is("array.txt");
        boost::archive::text_iarchive ia(is);

        // only deserialize initial array:
        boost::multi_array<int, 2> restored;
        ia >> restored;

        assert(restored != original); // entry overwritten with 999

        assert(restored.num_elements() == original.num_elements());
        auto [o_2_2, r_2_2] = std::mismatch(
                original.data(), original.data()+original.num_elements(),
                restored.data());

        assert(*o_2_2 == 999);
        assert(*r_2_2 == 20);

        // now patch in the sub array at the same sub-view:
        auto sub = restored[SLICE];
        ia >> sub;

        // now everything is equal
        assert(restored == original); // now matches!
        assert(*r_2_2 == 999);

        auto const& const_restored = restored;
        auto const_sub = const_restored[SLICE];
        //ia >> const_sub; // WON'T COMPILE
    }
}

如何通过 Boost.MPI 发送 2d Boost.MultiArray 的子数组？

How to send subarray of 2d Boost.MultiArray via Boost.MPI?

c++

boost

mpi

boost-multi-array

boost-mpi

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