How do I compile C++ file using the Eigen Library?

Question

I'm currently following this Eigen: Getting Started to try to compile my C++ file using the Eigen Library but I'm running into a bunch of errors. My current directory contains my main.cpp, network.h and the Eigen Library which contains a directory called Eigen and a bunch of other folders. The guide says to just put in the path to folder, containing the header files. I'm currently using g++ -I eigenLibrary/Eigen main.cpp -o network to compile, but I keep getting the error fatal error: 'Eigen/Dense' file not found #include <Eigen/Dense>. I'm trying implement the code in this tutorial . How can I make sure I'm linking the libraries in the right format. I don't have much experience with C++

EDIT: I've tried copying the Eigen subdirectory into /usr/local/include and running g++ -I /usr/local/include/Eigen/Dense main.cpp -o main to no success.

Hack06 · Accepted Answer · 2020-05-24 15:43:15Z

2

Please include the Eigen library path as follows:

g++ -std=c++11 -I /usr/include/eigen3/ fileName.cpp

edited May 24, 2020 at 15:43

Hack06

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answered May 24, 2020 at 14:46

Arjun Kumar

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Comments

Larry Gillstrom · Accepted Answer · 2017-02-11 23:05:55Z

0

Try -I eigenLibrary instead of -I eigenLibrary/Eigen in your command line

answered Feb 11, 2017 at 23:05

Larry Gillstrom

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5 Comments

lenignes Over a year ago

I've tried that previously. I keep getting ./network.h:17:21: error: expected ';' at end of declaration MatrixXd weights{ MatrixXd::Zero(i, j) };

Larry Gillstrom Over a year ago

so you tried that and you got past the problem with 'Eigen/Dense' file not found #include <Eigen/Dense>?

lenignes Over a year ago

Yeah I did. But now I'm getting an error in this line of code - MatrixXd weights{ MatrixXd::Zero(i, j) }; return weights;

Larry Gillstrom Over a year ago

I don't understand why you down voted my answer when it actually solved the question you asked...

lenignes Over a year ago

I didn't downvote your answer. I'm not sure who did. Also, I haven't fixed my code yet. Haven't been able to fix the error i mentioned above

ggulgulia · Accepted Answer · 2021-04-18 10:57:02Z

Eigen3 headers is by default installed under /usr/include/eigen3 directories To compile a program using Eigen3

a solution suggested by @Arjun Kumar could be used
to save tedious typing every time during compiling, a symbolic link inside /usr/local/include can be added to point to /user/include/eigen3 be made:
```
sudo ln -s /usr/include/eigen3/Eigen /usr/local/include/Eigen 
```

and then compile the program without any flags like:

 g++ -std=c++11 fileName.cpp

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