Eigen (C++ library)

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Eigen is a template header-only C++ linear algebra library. It is one of the fastest and most popular.

Website

Usage

Compilation

Reference
For optimal performance, I recommend using the following flags when compiling.

GCC

  • -mfma Enable fused multiply add
  • -mavx2 Enable avx2 vector instructions
  • -DEIGEN_NO_DEBUG Set preprocessor define for eigen optimizations
  • -fopenmp OpenMP parallel execution

Data to Eigen

You can use Eigen::Map to create an eigen view for your existing data.

Math

SVD

Eigen comes with a few SVD implementations in its SVD Module.
If you only need low-rank approximations then you may be interested in randomized SVD.
This can be 10-20x faster when calculating low-rank approximations on large matrices.
Github Implementation
Finding structure with randomness paper
Facebook Blog post