My name is Reid Atcheson. I have a PhD in Computational and Applied Mathematics (CAAM) from Rice University. I am a senior technical consultant for Numerical Algorithms Group (NAG). I periodically write here about my interests. I have interest in the following:

- Scientific computation and numerical analysis
- High performance computing
- Correctness of numerical algorithms
- Functional programming

07 Feb 2021 Visualizing Nested Dissection

07 Feb 2021 Nested Dissection for Sparse QR Factorization (video)

03 Feb 2021 Compressing the Sparse QR Factorization with Nested Dissection and Block Low-Rank Approximation

27 Jan 2021 An Interesting Inverse Inequality: Proof

24 Jan 2021 Conjecture Proven: New arXiv Manuscript Up

11 Jan 2021 Does QR Factorization Solve Linear Systems More Accurately Than Dense LU Factorization?

13 Nov 2020 Research in Progress: Nested Dissection Sparse QR Factorization

23 Oct 2020 Characterizing GMRES Convergence Part 1.4: Preconditioning Example

16 Oct 2020 Characterizing GMRES Convergence Part 1: Not Just Conditioning

21 Jul 2020 Waning Sars-Cov2 Immunity, Yet Another SIR Model

28 Apr 2020 Smoothing Covid19 Cases Data with Linear Programming

19 Oct 2019 Rust and C++ on Floating-point Intensive Code

18 May 2019 Recovering Sparsity from Noisy Data

21 Apr 2019 Fitting Noisy Data with Outliers

25 Mar 2019 Division Using only Multiply and Add

20 Mar 2019 7 Dubious Solutions to Approximate Floating-Point Equality

09 Mar 2019 Performance Results of Low-Rank Trick

03 Mar 2019 Quickly Discover Low-Rank Structure with GMRES

27 Feb 2019 Linear Algebra Secrets: Low Rank Updates

04 Aug 2018 I am a Below Average Quake Champions Player

26 May 2018 What to do when Julia's lufact runs out of memory

19 Mar 2018 Rice HPC Oil&Gas Conference 2018

15 Jan 2018 Estimating Errors in Summing Arrays of Floating Point Numbers

10 Jan 2018 Breaking Bayesian Inference

02 Jan 2018 Excluded Middle and the Stock Market

28 Dec 2017 Intermediate Value Theorem on Rational Numbers

14 Dec 2017 Computing Square Root of Rational Numbers

14 Nov 2017 Talk at SC17

02 Apr 2017 Rice HPC Oil&Gas Conference

22 Dec 2016 Abstract Numerical Linear Algebra: Update!

19 Oct 2016 Joint Post with Julia Computing

14 Oct 2016 Abstract Numerical Linear Algebra

27 Dec 2015 Running MPI Jobs on Google Compute Instances

07 Dec 2015 The danger of variable length arrays in C99+

12 Jul 2015 An International Mathematical Olympiad Problem

23 Apr 2015 I am a doctor now

07 Dec 2014 Infinitude of Primes Revisited

29 Aug 2014 JuliaCon Presentation

06 Jul 2014 Reciprocal Sum of Primes Diverges

04 Jul 2014 Infinitely many prime numbers: Euler's proof

10 Jan 2014 First website.