Feature/python bindings

.gitmodules

@@ -10,3 +10,6 @@
 [submodule "thirdparty/quickvec"]
 	path = thirdparty/quickvec
 	url = https://gitlab.lrz.de/IP/quickvec.git
+[submodule "thirdparty/pybind11"]
+	path = thirdparty/pybind11
+	url = https://github.com/pybind/pybind11.git

CMakeLists.txt

@@ -26,6 +26,7 @@ option(ELSA_INSTALL "Enable generating the install targets for make install" ${E
 option(ELSA_BUILD_EXAMPLES "Enable building of examples" ${ELSA_MASTER_PROJECT})
 
 option(ELSA_BUILD_CUDA_PROJECTORS "Enable building (or attempting to) the CUDA projectors" ON)
+option(ELSA_BUILD_PYTHON_BINDINGS "Attempt to build python bindings if enabled (required libclang-dev)" ON)
 option(ELSA_BUILD_WITH_MORE_WARNINGS "Enable all and extra warnings when building (-Wall -Wextra)" ON)
 
 option(ELSA_CUDA_VECTOR "Build elsa with GPU DataContainer support and default" OFF)
@@ -87,6 +88,7 @@ set(INSTALL_CONFIG_DIR ${CMAKE_INSTALL_LIBDIR}/cmake/elsa)
 # include the InstallElsaModule function
 include(InstallElsaModule)
 
+add_subdirectory(thirdparty/pybind11)
 
 # ------------ setup VectorCUDA --------
 # ------------
@@ -171,6 +173,11 @@ endif(ELSA_TESTING OR ELSA_BENCHMARKS)
 # ------------ add code/docs -----------
 # ------------
 
+# the bindings generator should be added before elsa, as we check whether the target can be built
+if (ELSA_BUILD_PYTHON_BINDINGS)
+    add_subdirectory(tools/bindings_generation EXCLUDE_FROM_ALL)
+endif()
+
 # the elsa library
 add_subdirectory(elsa)
 

cmake/FindLibClang.cmake

+find_program(LLVM_CONFIG_FOUND "llvm-config")
+if (LLVM_CONFIG_FOUND)
+  execute_process(
+    COMMAND llvm-config --cxxflags
+    OUTPUT_VARIABLE LibClang_Flags)
+
+  string(STRIP ${LibClang_Flags} LibClang_Flags)
+  separate_arguments(LibClang_Flags NATIVE_COMMAND ${LibClang_Flags})
+
+  execute_process(
+    COMMAND llvm-config --includedir
+    OUTPUT_VARIABLE LibClang_INCLUDE_DIR)
+
+  find_library(LibClangCpp_LIBRARY NAMES clang-cpp PATH_SUFFIXES llvm-9/lib llvm-10/lib)
+  find_library(LibLLVM_LIBRARY NAMES LLVM PATH_SUFFIXES llvm-9/lib llvm-10/lib)
+
+  set(LibClang_LIBRARIES ${LibClangCpp_LIBRARY} ${LibLLVM_LIBRARY})
+  set(LibClang_INCLUDE_DIRS ${LibClang_INCLUDE_DIR})
+
+  include(FindPackageHandleStandardArgs)
+  find_package_handle_standard_args(LibClang DEFAULT_MSG LibClang_LIBRARIES LibClang_INCLUDE_DIR)
+else()
+  message(WARNING "llvm-config couln't be located. Python bindings will not be generated")
+endif()
\ No newline at end of file

elsa/CMakeLists.txt

@@ -30,6 +30,47 @@ macro(ELSA_TEST NAME)
     catch_discover_tests(test_${NAME} TEST_SPEC ${ELSA_JUNIT_ARGUMENTS})
 endmacro(ELSA_TEST)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+    find_package(PythonLibs)
+    if(PYTHONLIBS_FOUND)
+        add_custom_target(pyelsa)
+
+        # macro for generation of the corresponding python module for the elsa target TARGET_NAME
+        # as a pre-build step the code for the python bindings will be generated and stored in BINDINGS_CODE_PATH
+        # the sources containing the public interface of TARGET_NAME should be specified as additional arguments
+        # you can omit a source file from the list to prevent the generation of bindings for that file
+        macro(GENERATE_BINDINGS TARGET_NAME BINDINGS_CODE_PATH HINTS_PATH)
+            if (TARGET pybind11_generator)
+
+            get_filename_component(CMAKE_CURRENT_LIST_DIR_LAST_PART ${CMAKE_CURRENT_LIST_DIR} NAME)
+                file(APPEND ${PROJECT_BINARY_DIR}/elsa/__init__.py "from .${CMAKE_CURRENT_LIST_DIR_LAST_PART} import *\n")
+
+                add_custom_command(OUTPUT ${BINDINGS_CODE_PATH}
+                    COMMAND ${PROJECT_BINARY_DIR}/tools/bindings_generation/pybind11_generator
+                        ${ARGN}
+                        --extra-arg=-I${PYTHON_INCLUDE_DIRS}
+                        --extra-arg=-I${PYBIND11_INCLUDE_DIR}
+                        --hints=${HINTS_PATH}
+                        -o=${BINDINGS_CODE_PATH}
+                        --name=${TARGET_NAME}
+                    DEPENDS ${TARGET_NAME} pybind11_generator ${HINTS_PATH}
+                    WORKING_DIRECTORY ${CMAKE_CURRENT_LIST_DIR}
+                    COMMENT "Generating bindings code for ${TARGET_NAME}"
+                    VERBATIM)
+
+                pybind11_add_module(py${TARGET_NAME} ${BINDINGS_CODE_PATH})
+                target_include_directories(py${TARGET_NAME} PUBLIC ${PROJECT_SOURCE_DIR}/elsa/bindings/hints)
+                target_link_libraries(py${TARGET_NAME} PUBLIC ${TARGET_NAME})
+                target_compile_features(py${TARGET_NAME} PUBLIC cxx_std_17)
+                add_dependencies(pyelsa py${TARGET_NAME})
+            endif()
+        endmacro()
+    else()
+        message(STATUS "Couldn't find Python.h. Python bindings will not be generated.")
+    endif()
+endif()
+
+
 # add the elsa modules
 add_subdirectory(core)
 add_subdirectory(logging)

elsa/core/CMakeLists.txt

@@ -89,6 +89,28 @@ target_compile_features(${ELSA_MODULE_TARGET_NAME} PUBLIC cxx_std_17)
 # set -fPIC
 set_target_properties(${ELSA_MODULE_TARGET_NAME} PROPERTIES POSITION_INDEPENDENT_CODE ON)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+    set(BINDINGS_SOURCES ${MODULE_SOURCES}
+        Descriptors/DataDescriptor.h
+        Descriptors/DescriptorUtils.h
+        Descriptors/VolumeDescriptor.h
+        Descriptors/BlockDescriptor.h
+        Descriptors/IdenticalBlocksDescriptor.h
+        Descriptors/PartitionDescriptor.h
+        Descriptors/RandomBlocksDescriptor.h
+        Geometry.h)
+        
+    list(FILTER BINDINGS_SOURCES EXCLUDE REGEX DataHandler.*.cpp)
+    list(FILTER BINDINGS_SOURCES EXCLUDE REGEX .*Descriptor.*.cpp)
+    list(FILTER BINDINGS_SOURCES EXCLUDE REGEX Geometry.cpp)
+    list(FILTER BINDINGS_SOURCES EXCLUDE REGEX StrongTypes.cpp)
+    
+
+    GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+            ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+            bindings_hints.hpp
+            ${BINDINGS_SOURCES})
+endif()
 
 # build the tests (if enabled)
 if(ELSA_TESTING)

elsa/core/bindings_hints.hpp

+#include "DataContainer.h"
+#include "Descriptors/VolumeDescriptor.h"
+#include "LinearOperator.h"
+#include "DescriptorUtils.h"
+
+#include <pybind11/pybind11.h>
+#include <pybind11/operators.h>
+
+#include <functional>
+
+namespace elsa
+{
+    template <typename Class>
+    struct ClassHints {
+    };
+
+    namespace py = pybind11;
+
+    /// wrapper for variadic functions
+    template <typename T, std::size_t N, typename = std::make_index_sequence<N>>
+    struct invokeBestCommonVariadic;
+
+    template <typename T, std::size_t N, std::size_t... S>
+    struct invokeBestCommonVariadic<T, N, std::index_sequence<S...>> {
+        static auto exec(const py::args& args)
+        {
+            if (args.size() == N)
+                return elsa::bestCommon(args[S].template cast<T>()...);
+
+            if constexpr (N > 1) {
+                return invokeBestCommonVariadic<T, N - 1>::exec(args);
+            } else {
+                throw(std::logic_error("Unsupported number of variadic arguments"));
+            }
+        };
+    };
+
+    template <typename data_t>
+    LinearOperator<data_t> adjointHelper(const LinearOperator<data_t>& op)
+    {
+        return adjoint(op);
+    }
+
+    template <typename data_t>
+    LinearOperator<data_t> leafHelper(const LinearOperator<data_t>& op)
+    {
+        return leaf(op);
+    }
+
+    // define global variables and functions in the module hints
+    struct ModuleHints {
+        static void addCustomFunctions(py::module& m)
+        {
+            m.def("adjoint", &adjointHelper<float>)
+                .def("adjoint", &adjointHelper<double>)
+                .def("adjoint", &adjointHelper<std::complex<float>>)
+                .def("adjoint", &adjointHelper<std::complex<double>>);
+
+            m.def("leaf", &leafHelper<float>)
+                .def("leaf", &leafHelper<double>)
+                .def("leaf", &leafHelper<std::complex<float>>)
+                .def("leaf", &leafHelper<std::complex<double>>);
+
+            m.def("bestCommon", (std::unique_ptr<DataDescriptor>(*)(
+                                    const std::vector<const DataDescriptor*>&))(&bestCommon))
+                .def("bestCommon", &invokeBestCommonVariadic<const DataDescriptor&, 10>::exec);
+        }
+    };
+
+    template <typename data_t, typename type_, typename... options>
+    void addOperatorsDc(py::class_<type_, options...>& c)
+    {
+        c.def(
+             "__add__",
+             [](const DataContainer<data_t>& self, const DataContainer<data_t>& other) {
+                 return DataContainer<data_t>(self + other);
+             },
+             py::return_value_policy::move)
+            .def(
+                "__mul__",
+                [](const DataContainer<data_t>& self, const DataContainer<data_t>& other) {
+                    return DataContainer<data_t>(self * other);
+                },
+                py::return_value_policy::move)
+            .def(
+                "__sub__",
+                [](const DataContainer<data_t>& self, const DataContainer<data_t>& other) {
+                    return DataContainer<data_t>(self - other);
+                },
+                py::return_value_policy::move)
+            .def(
+                "__truediv__",
+                [](const DataContainer<data_t>& self, const DataContainer<data_t>& other) {
+                    return DataContainer<data_t>(self / other);
+                },
+                py::return_value_policy::move)
+            // TODO: make the generator automatically generate this __setitem__ function
+            .def("__setitem__", [](elsa::DataContainer<data_t>& dc, elsa::index_t i, data_t value) {
+                dc[i] = value;
+            });
+    }
+
+    template <typename data_t>
+    struct DataContainerHints : public ClassHints<elsa::DataContainer<data_t>> {
+        constexpr static std::tuple ignoreMethods = {
+            "operator()", "begin", "cbegin", "end", "cend", "rbegin", "crbegin", "rend", "crend"};
+
+        template <typename type_, typename... options>
+        static void addCustomMethods(py::class_<type_, options...>& c)
+        {
+            addOperatorsDc<data_t>(c);
+        }
+
+        template <typename type_, typename... options>
+        static void exposeBufferInfo(py::class_<type_, options...>& c)
+        {
+            c.def(py::init([](py::buffer b) {
+                 py::buffer_info info = b.request();
+
+                 if (info.format != py::format_descriptor<data_t>::format())
+                     throw std::invalid_argument("Incompatible scalar types");
+
+                 elsa::IndexVector_t coeffsPerDim(info.ndim);
+
+                 ssize_t minStride = info.strides[0];
+                 for (std::size_t i = 0; i < static_cast<std::size_t>(info.ndim); i++) {
+                     if (info.strides[i] < minStride)
+                         minStride = info.strides[i];
+
+                     coeffsPerDim[static_cast<elsa::index_t>(i)] =
+                         static_cast<elsa::index_t>(info.shape[i]);
+                 }
+
+                 if (static_cast<std::size_t>(minStride) / sizeof(data_t) != 1)
+                     throw std::invalid_argument("Cannot convert strided buffer to DataContainer");
+
+                 auto map = Eigen::Map<Eigen::Matrix<data_t, Eigen::Dynamic, 1>>(
+                     static_cast<data_t*>(info.ptr), coeffsPerDim.prod());
+
+                 elsa::VolumeDescriptor dd{coeffsPerDim};
+
+                 return std::make_unique<elsa::DataContainer<data_t>>(dd, map);
+             })).def_buffer([](elsa::DataContainer<data_t>& m) {
+                std::vector<ssize_t> dims, strides;
+                auto coeffsPerDim = m.getDataDescriptor().getNumberOfCoefficientsPerDimension();
+                ssize_t combined = 1;
+                for (int i = 0; i < coeffsPerDim.size(); i++) {
+                    dims.push_back(coeffsPerDim[i]);
+                    strides.push_back(combined * static_cast<ssize_t>(sizeof(data_t)));
+                    combined *= coeffsPerDim[i];
+                }
+                return py::buffer_info(
+                    &m[0], sizeof(data_t), py::format_descriptor<data_t>::format(),
+                    m.getDataDescriptor().getNumberOfDimensions(), coeffsPerDim, strides);
+            });
+        }
+    };
+
+    template <typename data_t>
+    struct LinearOperatorHints : public ClassHints<elsa::LinearOperator<data_t>> {
+
+        template <typename type_, typename... options>
+        static void addCustomMethods(py::class_<type_, options...>& c)
+        {
+            c.def(py::self + py::self).def(py::self * py::self);
+        }
+    };
+
+    template <typename data_t>
+    struct DataContainerComplexHints : public ClassHints<elsa::DataContainer<data_t>> {
+        constexpr static std::tuple ignoreMethods = {
+            "operator()", "begin", "cbegin", "end", "cend", "rbegin", "crbegin", "rend", "crend"};
+
+        template <typename type_, typename... options>
+        static void addCustomMethods(py::class_<type_, options...>& c)
+        {
+            addOperatorsDc<data_t>(c);
+        }
+
+        // TODO: pybind11 does not provide a default format_descriptor for complex types -> make a
+        // custom one for this to work
+        // CustomMethod<true, py::buffer_info, elsa::DataContainer<data_t>&> buffer =
+        //     [](elsa::DataContainer<data_t>& m) {
+        //         std::vector<ssize_t> dims, strides;
+        //         auto coeffsPerDim = m.getDataDescriptor().getNumberOfCoefficientsPerDimension();
+        //         ssize_t combined = 1;
+        //         for (int i = 0; i < coeffsPerDim.size(); i++) {
+        //             dims.push_back(coeffsPerDim[i]);
+        //             strides.push_back(combined * static_cast<ssize_t>(sizeof(data_t)));
+        //             combined *= coeffsPerDim[i];
+        //         }
+        //         return py::buffer_info(
+        //             &m[0],          /* Pointer to buffer */
+        //             sizeof(data_t), /* Size of one scalar */
+        //             py::format_descriptor<data_t>::format(),
+        //             /* Python struct-style format descriptor
+        //              */
+        //             m.getDataDescriptor().getNumberOfDimensions(), /* Number of dimensions */
+        //             coeffsPerDim,                                  /* Buffer dimensions */
+        //             strides);
+        //     };
+    };
+
+    template struct DataContainerHints<float>;
+    template struct DataContainerComplexHints<std::complex<float>>;
+    template struct DataContainerHints<double>;
+    template struct DataContainerComplexHints<std::complex<double>>;
+    template struct DataContainerHints<index_t>;
+    template struct LinearOperatorHints<float>;
+    template struct LinearOperatorHints<double>;
+    template struct LinearOperatorHints<std::complex<float>>;
+    template struct LinearOperatorHints<std::complex<double>>;
+} // namespace elsa
\ No newline at end of file

elsa/functionals/CMakeLists.txt

@@ -61,6 +61,12 @@ if(ELSA_TESTING)
     add_subdirectory(tests)
 endif(ELSA_TESTING)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES})
+endif()
 
 # register the module
 registerComponent(${ELSA_MODULE_NAME})

elsa/generators/CMakeLists.txt

@@ -43,6 +43,12 @@ if(ELSA_TESTING)
     add_subdirectory(tests)
 endif(ELSA_TESTING)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES} CircleTrajectoryGenerator.h)
+endif()
 
 # register the module
 registerComponent(${ELSA_MODULE_NAME})

elsa/io/CMakeLists.txt

@@ -37,6 +37,17 @@ target_compile_features(${ELSA_MODULE_TARGET_NAME} PUBLIC cxx_std_17)
 # set -fPIC
 set_target_properties(${ELSA_MODULE_TARGET_NAME} PROPERTIES POSITION_INDEPENDENT_CODE ON)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        set(BINDINGS_SOURCES ${MODULE_SOURCES})
+
+        list(FILTER BINDINGS_SOURCES EXCLUDE REGEX ioUtils.cpp)
+        
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                bindings_hints.hpp
+                ${BINDINGS_SOURCES})
+endif()
+
 
 # build the tests (if enabled)
 if(ELSA_TESTING)

elsa/io/bindings_hints.hpp

+#include "EDFHandler.h"
+#include "MHDHandler.h"
+
+#include <pybind11/pybind11.h>
+
+#include <functional>
+
+namespace elsa
+{
+    template <typename Class>
+    struct ClassHints {
+    };
+
+    template <class Return, class... Args>
+    using CustomMethod = std::pair<bool, std::function<Return(Args...)>>;
+
+    namespace py = pybind11;
+
+    struct EDFHints : public ClassHints<EDF> {
+        constexpr static std::tuple ignoreMethods = {"read"};
+
+        template <typename type_, typename... options>
+        static void addCustomMethods(py::class_<type_, options...>& c)
+        {
+            c.def_static(
+                 "readf", [](std::string filename) { return EDF::read<float>(filename); },
+                 py::return_value_policy::move)
+                .def_static(
+                    "readd", [](std::string filename) { return EDF::read<double>(filename); },
+                    py::return_value_policy::move)
+                .def_static(
+                    "readl", [](std::string filename) { return EDF::read<index_t>(filename); },
+                    py::return_value_policy::move);
+        }
+    };
+
+    struct MHDHints : public ClassHints<MHD> {
+        constexpr static std::tuple ignoreMethods = {"read"};
+
+        template <typename type_, typename... options>
+        static void addCustomMethods(py::class_<type_, options...>& c)
+        {
+            c.def_static(
+                 "readf", [](std::string filename) { return MHD::read<float>(filename); },
+                 py::return_value_policy::move)
+                .def_static(
+                    "readd", [](std::string filename) { return MHD::read<double>(filename); },
+                    py::return_value_policy::move)
+                .def_static(
+                    "readl", [](std::string filename) { return MHD::read<index_t>(filename); },
+                    py::return_value_policy::move);
+        }
+    };
+} // namespace elsa
\ No newline at end of file

elsa/operators/BlockLinearOperator.h

@@ -75,6 +75,8 @@ namespace elsa
         /// default destructor
         ~BlockLinearOperator() override = default;
 
+        BlockLinearOperator& operator=(BlockLinearOperator&) = delete;
+
         /// return the operator corresponding to the i-th block of the matrix
         const LinearOperator<data_t>& getIthOperator(index_t i) const;
 

elsa/operators/CMakeLists.txt

@@ -52,6 +52,12 @@ if(ELSA_TESTING)
     add_subdirectory(tests)
 endif(ELSA_TESTING)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES})
+endif()
 
 # register the module
 registerComponent(${ELSA_MODULE_NAME})

elsa/problems/CMakeLists.txt

@@ -47,6 +47,12 @@ if(ELSA_TESTING)
     add_subdirectory(tests)
 endif(ELSA_TESTING)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES})
+endif()
 
 # register the module
 registerComponent(${ELSA_MODULE_NAME})

elsa/projectors/CMakeLists.txt

@@ -58,6 +58,12 @@ if(ELSA_TESTING)
     add_subdirectory(tests)
 endif(ELSA_TESTING)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES})
+endif()
 
 # register the module
 registerComponent(${ELSA_MODULE_NAME})

elsa/projectors_cuda/CMakeLists.txt

@@ -55,7 +55,13 @@ if (CMAKE_CUDA_COMPILER)
         add_subdirectory(tests)
     endif(ELSA_TESTING)
 
-
+    if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES})
+    endif()
+    
     # register the module
     registerComponent(${ELSA_MODULE_NAME})
 

elsa/solvers/CMakeLists.txt

@@ -43,6 +43,12 @@ if(ELSA_TESTING)
     add_subdirectory(tests)
 endif(ELSA_TESTING)
 
+if (ELSA_BUILD_PYTHON_BINDINGS)
+        GENERATE_BINDINGS(${ELSA_MODULE_TARGET_NAME}
+                ${CMAKE_CURRENT_BINARY_DIR}/bind_${ELSA_MODULE_NAME}.cpp
+                ""
+                ${MODULE_SOURCES})
+endif()
 
 # register the module
 registerComponent(${ELSA_MODULE_NAME})

pybind11 @ d96c3451

+Subproject commit d96c34516d276f4c33d25df23d5934af1c5b2406

tools/bindings_generation/CMakeLists.txt

+cmake_minimum_required(VERSION 3.10)
+
+find_package(LibClang)
+
+if (LIBCLANG_FOUND)
+    add_executable(pybind11_generator Parser.cpp)
+    target_compile_options(pybind11_generator PUBLIC ${LibClang_Flags})
+    target_compile_features(pybind11_generator PUBLIC cxx_std_17)
+    target_link_libraries(pybind11_generator LLVM clang-cpp stdc++fs)
+
+    file(WRITE ${PROJECT_BINARY_DIR}/elsa/__init__.py "")
+else()
+    message(WARNING "libclang-dev not found. Python bindings will not be generated.")
+endif()

tools/bindings_generation/Generator.hpp

+#pragma once
+
+#include "Module.h"
+
+#include <iostream>
+#include <fstream>
+#include <map>
+#include <algorithm>
+#include <assert.h>
+
+// Determine wether to use <filesystem> or <experimental/filesystem>. Adapted from
+// https://stackoverflow.com/questions/53365538/how-to-determine-whether-to-use-filesystem-or-experimental-filesystem,
+// simplified by removing MSVC specific code, as this is expected to be run with clang
+
+// We haven't checked which filesystem to include yet
+#ifndef INCLUDE_STD_FILESYSTEM_EXPERIMENTAL
+
+// Check for feature test macro for <filesystem>
+#if defined(__cpp_lib_filesystem)
+#define INCLUDE_STD_FILESYSTEM_EXPERIMENTAL 0
+
+// Check for feature test macro for <experimental/filesystem>
+#elif defined(__cpp_lib_experimental_filesystem)
+#define INCLUDE_STD_FILESYSTEM_EXPERIMENTAL 1
+
+// We can't check if headers exist...
+// Let's assume experimental to be safe
+#elif !defined(__has_include)
+#define INCLUDE_STD_FILESYSTEM_EXPERIMENTAL 1
+
+// Check if the header "<filesystem>" exists
+#elif __has_include(<filesystem>)
+#define INCLUDE_STD_FILESYSTEM_EXPERIMENTAL 0
+
+// Check if the header "<filesystem>" exists
+#elif __has_include(<experimental/filesystem>)
+#define INCLUDE_STD_FILESYSTEM_EXPERIMENTAL 1
+
+// Fail if neither header is available with a nice error message
+#else
+#error Could not find system header "<filesystem>" or "<experimental/filesystem>"
+#endif
+
+// We priously determined that we need the exprimental version
+#if INCLUDE_STD_FILESYSTEM_EXPERIMENTAL
+// Include it
+#include <experimental/filesystem>
+
+// We need the alias from std::experimental::filesystem to std::filesystem
+namespace std
+{