如何设置CMakeLists.txt文件以启动并运行xtensor-python示例代码

Question

I'm trying to use xtensor-python example found here .

I have xtensor-python, pybind11, and xtensor installed and also created a CMakeLists.txt.

from /build I ran. $ cmake .. $ make

and it builds without errors.

My CMakeLists.txt looks like this.

cmake_minimum_required(VERSION 3.15)
project(P3)

find_package(xtensor-python REQUIRED)
find_package(pybind11 REQUIRED)
find_package(xtensor REQUIRED)

My example.cpp file.

#include <numeric>                        // Standard library import for std::accumulate
#include "pybind11/pybind11.h"            // Pybind11 import to define Python bindings
#include "xtensor/xmath.hpp"              // xtensor import for the C++ universal functions
#define FORCE_IMPORT_ARRAY                // numpy C api loading
#include "xtensor-python/pyarray.hpp"     // Numpy bindings

double sum_of_sines(xt::pyarray<double>& m)
{
    auto sines = xt::sin(m);  // sines does not actually hold values.
    return std::accumulate(sines.cbegin(), sines.cend(), 0.0);
}

PYBIND11_MODULE(ex3, m)
{
    xt::import_numpy();
    m.doc() = "Test module for xtensor python bindings";

    m.def("sum_of_sines", sum_of_sines, "Sum the sines of the input values");
}

My python file.

import numpy as np
import example as ext

a = np.arange(15).reshape(3, 5)
s = ext.sum_of_sines(v)
s

But my python file can't import my example.cpp file.

  File "examplepyth.py", line 2, in <module>
    import example as ext
ImportError: No module named 'example'

I am new to cmake. I would like to know how to set this project up properly with CMakeLists.txt

Answer 1

The recommended way is to build and install with a setup.py file instead of cmake. You can use the cookie-cutter to get the boilerplate generated for you.

Answer 2

Hey I am not sure about xtensor-python since I have not used it, but I might give you some pointers for building pybind11 with cmake within an Anaconda environment. Your Cmake.txt looks a bit incomplete. For me the following set-up works:

In my Anaconda-shell I use the following commands:

cmake -S <folder where Cmake.txt is> B <folder where Cmake.txt is\build> -G"Visual Studio 15 2017 Win64" 

which puts all the linking into the subfolder build, so the actual building can be done via

cmake --build build

The necessary Cmake.txt looks something like below. The created library TEST is then located in the subfolder debug\\Build

#minimum version of cmake
cmake_minimum_required(VERSION 2.8.12)
#setup project
project(TEST)

#load the libraries
find_package(pybind11 REQUIRED)
set(EXTERNAL_LIBRARIES_ROOT_PATH  <Filepath where my external libraries are at>)
set(EIGEN3_INCLUDE_DIR ${EXTERNAL_LIBRARIES_ROOT_PATH}/eigen-eigen-c753b80c5aa6) 

#get all the files in the folder
file(GLOB SOURCES
    ${CMAKE_CURRENT_SOURCE_DIR}/*.h
    ${CMAKE_CURRENT_SOURCE_DIR}/*.cpp   
)
#include the directories
include_directories(${PYTHON_INCLUDE_DIRS} ${pybind11_INCLUDE_DIRS} ${EIGEN3_INCLUDE_DIR})

pybind11_add_module(TEST MODULE ${SOURCES})

#in some cases need to link the libraries 
#target_link_libraries(TEST PUBLIC ${OpenCV_LIBRARIES} ${Boost_LIBRARIES})  

If you want a working minimal example for which I use exactly this Cmake.txt file, it happens to be in another question I posted here on stackoverflow: pybind11 how to use custom type caster for simple example class

Hope this helps as a first starting point (I left the EIGEN3 inside as to give you an idea how it is done with a header-only library. For actual libraries like OpenCV you need the target_link_libraries command in addition).