CODEWITHSUNDEEP
indexingeigenpybind11
Moshe Bouhnik
Moshe Bouhnik

Reputation: 11

Eigen::placeholders::all for Eigen array/matrix with pybind11

I am building a c++ program linked to python code, using pybind11. I use Eigen for the matrix operations. I am having issues with the slicing of an Eigen array. According to Eigen documentation, it is possible to slice an array using Eigen::placeholders::all -

std::vector<int> ind{4,2,5,5,3};
MatrixXi A = MatrixXi::Random(4,6);
cout << "Initial matrix A:\n" << A << "\n\n";
cout << "A(all,ind):\n" << A(Eigen::placeholders::all,ind) << "\n\n";

However, when I try to use this syntax in my code, I get the following error:

error: ‘Eigen::indexing’ has not been declared

I found an explanation for this - The Eigen header I used is of pybind11, not the original Eigen header. This explains the issue, but not helping with a solution.

I tried including the original Eigen headers, but it won't include the indexing or placeholders namespaces.

Thank for your assistance!

edit: Here is the code I tried to compile:

#include <pybind11/pybind11.h>
#include <pybind11/eigen.h>
#include <pybind11/stl.h>
#include <pybind11/numpy.h>
#include <pybind11/iostream.h>
#include <iostream>
#include <valarray>
#include <Eigen/Core>


namespace py = pybind11;



void example()
{
    std::vector<int> ind{4,2,5,5,3};
    Eigen::MatrixXi A = Eigen::MatrixXi::Random(4,6);
    std::cout << "Initial matrix A:\n" << A << "\n\n";
    std::cout << "A(all,ind):\n" << A(Eigen::placeholders::all,ind) << "\n\n";
}

For which I got the following error:

error: ‘Eigen::placeholders’ has not been declared

Upvotes: 0

Views: 558

Answers (1)

Moshe Bouhnik
Moshe Bouhnik

Reputation: 11

Eventually I was able to solve the issue - it was an issue with the cmake files, and specifically, the FindEigen3.cmake was missing under the cmake folder. Somehow, (probably because of pybind11/Eigen header) the program was able to compile, but could not find all the relevant headers. After adding the FindEigen3.cmake under the cmake folder, all included folders were correct, and I could use Eigen::placeholders::all. Thanks @Homer512 for the assistance!

Upvotes: 1

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