Boost.Multi

Boost.Multi provides owning multidimensional arrays containers and non-owning multidimensional views for C++17. It supports slicing, layout transformations, and CPU/GPU memory.

Project status: Boost.Multi is not an official or accepted Boost library. It is being proposed for inclusion in Boost and has no Boost-library dependencies.

© Alfredo A. Correa, 2018–2026

• Generic element type and dimensionality
• Natural multidimensional access: write A[i][j]... or iterate recursively over rows, subarrays or elements.
• Composable subarray views: slice, transpo se, rotate indices, and broadcast arrays without copying their elements.
• Interoperability: use standard algorithms (iterators and ranges), allocators, and legacy libraries for strided arrays (BLAS, FFTW, CUDA, HIP, MPI, etc.)

git clone https://github.com/correaa/boost-multi.git  # or gitlab.com/correaa/boost-multi.git
cd boost-multi
cmake -S . -B build
cmake --build build
ctest --test-dir build --output-on-failure

Read the documentation or explore test/.

#include <cassert>
#include <multi/array.hpp>

namespace multi = boost::multi;

int main() {
    multi::array<int, 2> A = {
        {1, 2, 3},
        {4, 5, 6}
    };

    assert(A[1][1] == 5);  // ordinary multidimensional indexing

    using multi::_;
    auto&& second_column = A(_, 1);  // a non-owning view
    second_column[0] = 20;           // changes A[0][1]
    assert(A[0][1] == 20);
}

• Online documentation

Try the library online with Godbolt's Compiler Explorer.

Add the repository's include/ directory to your compiler's include path and include the headers you need:

#include <multi/array.hpp>

Alternatively, download the single amalgamated header and include it as #include <boost-multi.hpp>.

Add Multi from an in-tree source directory and link its interface target:

add_subdirectory(path/to/boost-multi)
target_link_libraries(my_target PRIVATE multi)

Fetch Multi on demand:

include(FetchContent)
FetchContent_Declare(multi GIT_REPOSITORY https://gitlab.com/correaa/boost-multi.git)
FetchContent_MakeAvailable(multi)
target_link_libraries(my_target PRIVATE multi)

Testing requires Boost.Test. For example, install libboost-test-dev on Debian/Ubuntu or boost-devel on Fedora.

cmake -S . -B build
cmake --build build
ctest --test-dir build --output-on-failure

• File a Gitlab issue or Github issue.
• Join the #boost-multi discussion group at cpplang.slack.com