Eigen is a general-purpose linear algebra C++ library. In Eigen, all matrices and vectors are objects of the Matrix template class, and the vector is a specialization of the matrix type, with either one row or one column. Tensor objects are not presented in official APIs but exist as submodules.
We can define the type for a matrix with known dimensions and floating-point data type like this:
typedef Eigen::Matrix<float, 3, 3> MyMatrix33f;
We can define a vector in the following way:
typedef Eigen::Matrix<float, 3, 1> MyVector3f;
Eigen already has a lot of predefined types for vector and matrix objects—for example, Eigen::Matrix3f (floating-point 3x3 matrix type) or Eigen::RowVector2f (floating-point 1 x 2 vector type). Also, ...
