Top all-time · #2555
Fredrik Johansson
Personal blog · fredrikj.net/blog · on HN as fdejmathprogramming
Fredrik Johansson's personal blog at fredrikj.net covers math and programming. Since 2012, 29 different Hacker News readers have linked it 40 times, most often “Developing mathematical software in C (2021)”. It is still writing: the last post was on 2026-05-14, and you can follow it by feed.
Most-linked posts?
- Developing mathematical software in C (2021)3 people · 3 mentions · first linked 2021-01-28
- Calcium: Exact real and complex numbers in C2 people · 3 mentions · first linked 2022-02-07
- A Grimoire of Functions2 people · 3 mentions · first linked 2019-05-31
- /calcium/index.html2 people · 2 mentions · first linked 2023-02-07
- Arb: a C library for arbitrary-precision floating-point ball arithmetic2 people · 2 mentions · first linked 2013-11-02
- High-Precision Linear Algebra in Julia: BigFloat vs. Arb2 people · 2 mentions · first linked 2018-07-31
- Rigorous Numerical Integration in Arb (2017)2 people · 2 mentions · first linked 2024-06-26
What Hacker News says?
Great work! I like how well considered the design is. This calculator takes a point in the design space with text input, equation rendering, a grapher, and Big Int/Floats for number representation. I wonder if the author considered an input method where keypresses translate directly into a rendered equation? Symbolab kind of does this, so instead of writing an expression in some functional style and seeing its rende…
Comment linking /calcium/
on “Show HN: All desktop software calculators are wrong, so I had to build my own”Submitted A Grimoire of Functions as a story · 142 points
HN discussionThat's called ball arithmetic, and there are many libraries for it, such as arb. http://fredrikj.net/arb/ It's useful in mathematical calculation, but usually with floating point calculations you have some error bounds coming from your algorithm which are "good enough" if the result is going to be the value of something with 5% tolerance.
Comment linking /arb/
on “Why doesn't GCC optimize a*a*a*a*a*a to (a*a*a)*(a*a*a)? (2013)”Submitted Things I would like to see in a computer algebra system as a story · 130 points
HN discussionyou may find this interesting if you haven't seen it already: https://fredrikj.net/blog/2017/11/new-rigorous-numerical-int...
Comment linking /blog/2017/11/new-rigorous-numerical-integration-in-arb/
on “A brief introduction to interval arithmetic”Submitted New partition function record: p(10^20) computed as a story · 105 points
HN discussion>"When computers revealed all those smaller copies of the Mandelbrot set within itself, Douady and Hubbard wanted to explain their presence. They ended up turning to what’s known as renormalization theory , a technique that physicists use to tame infinities in the study of quantum field theories, and to connect different scales in the study of phase transitions." https://en.wikipedia.org/wiki/Renormalization Rampant…
Comment linking /blog/2009/12/analytic-continuation-of-3f2-4f3-and-higher-functions/
on “The quest to decode the Mandelbrot set”Submitted Printing Algebraic Numbers as a story · 87 points
HN discussionThe API itself is perhaps less interesting than the implementation strategy. I'm presently developing a C library for exact real and complex numbers ( http://fredrikj.net/calcium/ ) that goes much further to make equality decidable even in complicated cases while also enabling efficient computations. Still working on implementing functionality and writing up a formal paper.
Comment linking /calcium/
on “Toward an API for the Real Numbers”Submitted Computing Bell numbers as a story · 17 points
HN discussionAlso (shameless self-promotion) python-flint! http://fredrikj.net/python-flint/
Comment linking /python-flint/
on “Common Lisp: Numbers”Submitted Developing mathematical software in C (2021) as a story · 9 points
HN discussionThere is an algorithm by Richardson to prove equality of real and complex numbers composed from exponentials and logarithms. (It doesn't have a complete proof of correctness, but it never returns a wrong result: it will loop forever iff it encounters a counterexample to Schanuel's conjecture.) It can also be extended to higher transcendental functions, but it gets harder to guarantee termination. I have a library fo…
Comment linking /calcium/
on “Now I’m calculating with constructive reals”Submitted High-Precision Linear Algebra in Julia: BigFloat vs. Arb as a story · 6 points
HN discussionGood point. I added an RSS feed link to https://fredrikj.net/blog/ . I just hacked together some quick code to generate it, so let me know if it doesn't work.
Comment linking /blog/
on “Arb: Efficient Arbitrary-Precision Midpoint-Radius Interval Arithmetic (2016)”Submitted Developing Mathematical Software in C as a story · 5 points
HN discussionAuthor here. I will take the opportunity to advertise my blog at https://fredrikj.net/blog/ where I post occasional development updates about Arb and other projects. Some improvements not covered in the 2016 preprint include much faster code for arithmetic and matrix multiplication ( https://arxiv.org/abs/1901.04289 , https://fredrikj.net/blog/2018/07/high-precision-linear-alge... ), and code for rigorous arbitrary-…
Comment linking /blog/2017/11/new-rigorous-numerical-integration-in-arb/
on “Arb: Efficient Arbitrary-Precision Midpoint-Radius Interval Arithmetic (2016)”Submitted A Grimoire of Functions as a story · 5 points
HN discussion> When I started working on this I thought that I might want to switch to "binary coded decimal"[0] to avoid issues with inputs like (0.1 + 0.2 - 0.3). If you want to go this route, there are standardized decimal floating points, e.g. https://en.wikipedia.org/wiki/Decimal64_floating-point_forma... (or the 128 bit version). > And is there an implementation I could use? Afaik Boehms implementation lived only in the An…
Comment linking /
on “Show HN: AlexCalc, a scientific calculator with LaTeX equation display”Submitted Calcium: Exact real and complex numbers in C as a story · 4 points
HN discussionThere's a little bit more information in Fredrik J's blog post: http://fredrikj.net/blog/2015/09/finding-nemo/
Comment linking /blog/2015/09/finding-nemo/
on “Nemo: computer algebra package for Julia”Submitted Developing Mathematical Software in C as a story · 4 points
HN discussionjust yesterday someone commented about https://fredrikj.net/calcium/index.html which is pretty darn amazing. pi and e are essentially first class, but a lot of transcendentals aren't. seems like a really neat approach.
Comment linking /calcium/index.html
on “Why does 0.1 and 0.2 = 0.30000000000000004?”Submitted Computing with Metavalues as a story · 3 points
HN discussionHey, that's me! Though I mention it in the post, I also want to give a shoutout here to libcalcium, which handles the somewhat magical task of representing and comparing exact algebraic numbers: https://fredrikj.net/calcium/index.html .
Comment linking /calcium/index.html
on “The Quest to Find Rectangles in a Square”Submitted High-precision linear algebra in Julia: BigFloat vs. Arb (2018) as a story · 3 points
HN discussionSubmitted A Grimoire of Functions as a story · 3 points
HN discussionSubmitted Rigorous Numerical Integration in Arb (2017) as a story · 2 points
HN discussionSubmitted Citing Papers in Software (2021) as a story · 2 points
HN discussionSubmitted Arb Is 10 as a story · 2 points
HN discussion
