jjj.de

What it is

jjj.de is a personal technical resource site maintained by Jörg Arndt, described on the page itself as “useful and ugly pages.” Based on the crawled content, it is not a typical SaaS developer tool, but rather a resource index focused on algorithms, mathematical computation, and personal script/configuration files. Its core content includes the FXT library, FXT demos, FFT routines, bit operations and algorithms, Matters Computational, plane-filling curves, mathematical data tables, pari/gp scripts, as well as configurations for emacs, zsh/bash, X11/ctwm, and more.

Core capabilities and ecosystem

The site’s most valuable section is its low-level algorithm material. FXT demos are organized into categories such as arith, bits, comb, ds, fft, gf2n, graph, mod, perm, seq, and sort, covering topics including CORDIC, exponentiation, bit manipulation, combinatorial objects, data structures, fast Fourier and Walsh transforms, GF(2^n), graph search, modular arithmetic, permutations, integer sequences, and sorting/searching. It can be a useful reference for developers researching algorithm implementations, combinatorial generation, number-theoretic computation, or foundational signal-processing routines. In terms of ecosystem, the pages explicitly connect to OEIS, pari/gp, and common Unix toolchain configurations.

Pricing and openness

The crawled text does not show any subscription, purchase, or commercial licensing information, and the pages appear to be directly accessible, so it can be treated as a free resource site. However, the crawled content does not specify whether it is open source, the exact license, the licensing boundaries of the FXT library, or any self-hosting method, so you should not assume it can be used directly in commercial projects.

Pros and cons

The strengths are its highly specialized focus, broad coverage of low-level algorithms, lightweight pages, and high information density, making it suitable for experienced programmers who are willing to dig through directories. The downsides are also clear: the site interface is extremely plain, and it lacks modern search, package management, version notes, quick-start guides, and API/SDK documentation. The only visible support channel is the author’s email, and the site appears to be personally maintained, so enterprise-grade SLA should not be expected.

Who it is for and access from China

It is suitable for algorithm researchers, mathematical computing enthusiasts, and developers who need references for implementations of FFT, combinatorics, bit operations, finite fields, and number theory. It is not suitable for teams looking for ready-to-use cloud services, collaboration platforms, or commercially supported software. Access from China cannot be determined from the crawled text and is marked as unknown. If you need more engineering-oriented alternatives, consider FFTW, GSL, Boost, OEIS, GitHub algorithm repositories, and similar resources.