Wrap C++ function with Boost Python -- numpy array types

Question

From what I gather, a good way to do this is to use the Boot.Python library, like this simple example; please don't recommend alternatives like Cython as a solution. But when I try to use boost::python data types, my cpp file won't build.

example_boost.cpp:

#include <boost/python.hpp>
#include <boost/python/numpy.hpp>

#include <iostream>

namespace bpy = boost::python;
namespace bnp = boost::python::numpy;

void do_stuff(const bnp::ndarray& input_array) {
    ...
};

/*
 * This is a macro Boost.Python provides to signify a Python extension module. This enables me to import example_boost.cpp and call do_stuff() within a Python file. 
 */
BOOST_PYTHON_MODULE(crf) {
    // Expose the functions
    boost::python::def("compute_factor_out_msgs", compute_factor_out_msgs);
}

Running make...

Undefined symbols for architecture x86_64:
      "boost::python::converter::object_manager_traits<boost::python::numpy::ndarray>::get_pytype()", referenced from:
          boost::python::detail::caller_arity<1u>::impl<OutMessages (*)(boost::python::numpy::ndarray const&), boost::python::default_call_policies, boost::mpl::vector2<OutMessages, boost::python::numpy::ndarray const&> >::operator()(_object*, _object*) in example_boost.o
    ld: symbol(s) not found for architecture x86_64
    clang: error: linker command failed with exit code 1 (use -v to see invocation)
    make: *** [example_boost.so] Error 1

Notes:

make was successful if I don't use the bpy and bnp types, so my Makefile is correct.
I have Boost v 1.63.0 installed via homebrew, on Mac OSX El Capitan
Using C++ 11 and Python 2.7

make was successful if I don't use the bpy and bnp types, so my Makefile is correct. Nope, it misses the linker flags to the libraries providing the symbols in bpy and bnp. — Walter
– Walter, Commented May 19, 2017 at 16:17

Community · Accepted Answer · 2017-05-23 12:03:07Z

1

Two problems with the posted example code:

To resolve the make issue, the Makefile would have to also link -lboost_numpy.
Even though it would compile, the result would be a seg fault (stack overflow) because we need to first initialize with

Py_Initialize(); bnp::initialize();

as explained here.

edited May 23, 2017 at 12:03

CommunityBot

11 silver badge

answered Mar 6, 2017 at 0:04

BoltzmannBrain

5,49213 gold badges55 silver badges83 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Wrap C++ function with Boost Python -- numpy array types

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related