Linear-Algebra

Why You Should Use stableNorm() Instead of norm(): A Lesson from Eigen Code Review

A one-word review comment on my Eigen MR revealed that hand-rolling normalization with .norm() silently breaks on extreme inputs. Eigen already had the fix — I just wasn’t using it.

Upgrading Householder Right-Side: BLAS-2 to BLAS-3

Upgrading Eigen's Householder Right-Side Application from BLAS-2 to BLAS-3

Eigen’s blocked Householder path only existed for left-side application. I added the right-side equivalent, upgrading M*Q from O(n) rank-1 updates to cache-friendly blocked matrix multiplies.

Modified Gram-Schmidt vs Householder QR: A Performance Showdown in Eigen

I submitted a Modified Gram-Schmidt QR decomposition to Eigen and a maintainer asked: why? Here’s the benchmark data that answered the question.