Seamless operability between C++11 and Python / Matlab

This section is for enthusiastic students who want for example connect their embedded hardware and measuremnt directly into the scientific framework of Python or Matlab.

Python solution:

pybind11 is a lightweight header-only library that exposes C++ types in Python and vice versa, mainly to create Python bindings of existing C++ code.

Matlab solution:

You can call your own C or C++ programs from the MATLAB command line as if they were built-in functions. These programs are called MEX functions and the function name is the MEX file name.

Python pybind11

Python modul installation

pip3 install pybind11

Micky Mouse example

#include <pybind11/pybind11.h>

// Linux
// c++ -O3 -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)
// MacOS
// c++ -O3 -Wall -shared -std=c++11 -undefined dynamic_lookup $(python3 -m pybind11 --includes) example.cpp -o example$(python3-config --extension-suffix)

namespace py = pybind11;

int add(int i, int j) {
    return i + j;
}

PYBIND11_MODULE(example, m) {
    m.doc() = "pybind11 example plugin"; // optional module docstring

    m.def("add", &add, "A function which adds two numbers");
}

Binding to NumPy

The example shows an implementation of the tridiagonal solver in C/C++ with pybind11 binding to python3.

Build:
// Linux
c++ -O3 -Wall -shared -std=c++11 -fPIC $(python3 -m pybind11 - -includes) tridiagsolverNumpy.cpp -o tridiag$(python3-config - -extension-suffix)
// MacOS
c++ -O3 -Wall -shared -std=c++14 -undefined dynamic_lookup $(python3 -m pybind11 - -includes) tridiagsolverNumpy.cpp -o tridiag$(python3-config - -extension-suffix)
// Windows
have a look...

Download: tridiagsolverNumpy.cpp

Usage:
# import numpy
import numpy as np
# import the new solver from tridiag module:
from tridiag import solve

n = 50
ad = 2*np.ones(n)
al = -np.ones(n-1)
au = -np.ones(n-1)
b = 3*np.ones(n)

solve(ad, al, au, b)

array([ 75., 147., 216., 282., 345., 405., 462., 516., 567., 615., 660.,
       702., 741., 777., 810., 840., 867., 891., 912., 930., 945., 957.,
       966., 972., 975., 975., 972., 966., 957., 945., 930., 912., 891.,
       867., 840., 810., 777., 741., 702., 660., 615., 567., 516., 462.,
       405., 345., 282., 216., 147.,  75.])

Matlab MEX

The same example for the Matlab MEX interface. To build the code use in the matlab console:

mex tridiagsolverMEX.c

Download: