# Eigen C++ library

10 Hacker News commenters recommended Eigen C++ library and 4 criticized it, November 2025 to November 2026. It was recommended in 7 of 13 months. It meets the Hacker Approved badge rule.

**Verdict:** Fast C++ linear algebra library praised for performance and zero-cost abstractions; critics point to slow compiles and large binaries.

## Why people recommend it

- Performance with high-level readability (2 comments): "You get the readability of high-level code with the performance of low-level code thanks to the "zero-cost abstractions" of Eigen." ([source](https://news.ycombinator.com/item?id=46051424)) "I use the Eigen matrix library as a replacement for Numpy when I need more performance" ([source](https://news.ycombinator.com/item?id=46308950))

## What people warn about

- Long compile times (2 comments): "Eigen is one of the worst libraries when it comes to both exe size and compile times." ([source](https://news.ycombinator.com/item?id=46419047)) "This is also a bit reminiscent of the compile time issues with Eigen" ([source](https://news.ycombinator.com/item?id=45894392))
- Large binaries with debug symbols (2 comments): "Eigen is one of the worst libraries when it comes to both exe size and compile times." ([source](https://news.ycombinator.com/item?id=46419047)) "I've seen terrible, terrible binary sizes with Eigen + debug symbols" ([source](https://news.ycombinator.com/item?id=46418433))

## Alternatives hackers recommend

- [Intel MKL](https://hackerapproved.com/p/intel-mkl.md): 5 recommend
- [LAPACK](https://hackerapproved.com/p/lapack.md): 5 recommend

## Cite as

Hacker Approved, "Eigen C++ library", https://hackerapproved.com/p/eigen/ (counts from 1,795,640 Hacker News comments, November 2025 to November 2026).