Robert Clausecker

This is the page of Robert Clausecker. Send mail to fuz@fuz.su.

Areas of Interest

• SIMD algorithms engineering
• focus on discrete and combinatorial problems
• any architecture, with focus on AArch64 and x86-64
• SAT solvers
• performance engineering and program optimisation
• heuristic search for combinatorial optimisation and planning
• UNIX systems programming
• special focus on FreeBSD
• engineering for portability
• software development on/for vintage/legacy computers, systems, and peripherals
• assembly programming (any architecture)
• array oriented programming (APL, J)

Personal Projects

• dobutsu – tablebase and engine for Dōbutsu Shōgi (releases)
• 24puzzle – a program to solve the 24 puzzle
• sais-x86 – suffix array construction using the SA-IS algorithm in x86 assembly
• 8bc – B compiler for the PDP-8
• pospop – assembly-optimised positional population count routines for Go
• palanqin – ARM Cortex-M0 emulator for DOS
• memf – a family of C functions to marshal binary file formats and protocols
• fdup – file duplicate detection utility (currently broken, do not use!)
• various bindings for the Go programming language.
  • Go bindings for the libnfc
  • Go bindings for the libfreefare
  • Go bindings for the libopenkey
• rabinkarp – SIMD-accelerated Rabin-Karp hashing

Projects I Contribute to

• schilytools – Collection of tools and libraries by Jörg Schilling (maintainer, releases)
• simdutf – SIMD optimized Unicode routines
• mecrisp stellaris – native code Forth system for ARM (maintainer, releases, FreeBSD port, DOS port)
• FreeBSD Ports Collection (ports committer)
• FreeBSD libc (contributed SIMD-enhanced string functions)

Programs

• hacklace.c – flashing utility for the hacklace
• sb16_dsp.c.diff – a patch to make the SoundBlaster driver work on Minix 2.0.4
• golang.nanorc – configuration to highlight Go source files in Nano
• hierholzer.w – a literate C program to compute Eulerian tours (PDF render)
• wasteram.c – a program to waste a specified amount of RAM
• cksum – an implementation of cksum(1) for DOS
• nethack-361-ultrix.diff – a patch to make NetHack 3.6.1 run on an old MIPS box with ULTRIX 4.4
• split – a set of shell scripts to split file sets into equally sized parts
• utf8utf16avx512.tar.xz – supplementary code to the paper “Transcoding Unicode Characters with AVX-512 Instructions”

Files

• 1 000 000 000 000 digits of pi
• Schneider PC 7640 supplemental floppy disks
• Schneider PC 7640 HDD image (courtesy of Minki Avali)
• old versions of Agner Fog's objconv utility
• packages for armv7 FreeBSD 13 and 14 (pkg.conf, signing key)
• x86 instruction encoding cheat sheet (ODS)

Talks

• Haskell – eine etwas andere Sprache (German, Ubucon 2012, Berlin)
• Die Programmiersprache Go (German, LinuxTag 2013, Berlin)
• Heartbleed – Was war da eigentlich los? (German, BeLUG, 2014)
• Kernighan & Ritchie: Eine dramaturgische Lesung (German, BeLUG, 2015)
• Mein Umstieg auf FreeBSD (German, CLT 2016, Chemnitz)
• Maschinenprogrammierung auf x86-Linux für Anfänger (German, CLT 2018, Chemnitz)
• Better PDB Heuristics for Sliding Tile Puzzles (English, International Workshop on Pattern Databases and Large-Scale Search, Berlin, 2018)
• Datenträgerverwaltung unter FreeBSD (German, CLT 2019, Chemnitz)
• Building a B compiler for the PDP-8 (German, VCFB, 2019, recorded)
• Die Mikroarchitektur moderner Prozessoren: ein Crashkurs (German, Reconnect to Chaos, 2022, recorded)
• Die Mikroarchitektur moderner Prozessoren: ein Crashkurs (German, CLT 2023, Chemnitz)
• Softwarepaketierung unter FreeBSD (German, CLT 2024, Chemnitz)
• Textverarbeitung mit SIMD-Techniken (German, EH21, Regensburg, recorded)
• SIMD-enhanced libc string functions: how it's done (English, EuroBSDcon 2024, with Getz Mikalsen, Dublin, recorded)
• SIMD-Programmierung: Eine Einführung (German, CLT 2025, Chemnitz)
• SIMD-enhanced libc string functions: how it's done (English, Lund Linux Con 2025, Lund)

Publications

• 2017-07 ACSL By Example (with Jens Gerlach and others)
• 2017-11 Notes on the Construction of Pattern Databases (URN)
• 2019-07 Zero-Aware Pattern Databases with 1-Bit Compression for Sliding Tile Puzzles (slide deck, with Alexander Reinefeld)
• 2020-06 The Quality of Heuristic Functions for IDA* (URN)
• 2021-04 Angenehmes Blinken (with Matthias Koch)
• 2021-07 A Measure of Quality for IDA* Heuristics (slide deck, poster, with Florian Schintke)
• 2021-10 Angenehmes Blinken II (with Matthias Koch)
• 2023-09 Transcoding Unicode Characters with AVX-512 Instructions (with Daniel Lemire)
• 2023-11 Prioritised Unit Propagation by Partitioning the Watch Lists (slide deck, with Benjamin Kaiser and Michael Mavroskoufis)
• 2025-11 Faster Positional-Population Counts for AVX2, AVX-512, and ASIMD (with Daniel Lemire and Florian Schintke)
• 2026-01 Fixing ill-formed UTF-16 strings with SIMD instructions (preprint, with Daniel Lemire)
• 2026-06 Practical Parallel Block Tree Construction (with Florian Kurpicz and Etienne Palanga)
• 2026-07 Parallel O(√n) Overhead LSD Radix Sort (with Florian Schintke, supplementary material)

Awards

• Tag der Mathematik 2013 – 1st place “kleiner Abelpreis” (with Tilman Brämick, Yiyang Huang, and Deniz Leon Ochmann)
• SAT Competition 2021 – special innovation price (with Benjamin Kaiser)
• SoCS 2021 – best paper award (with Florian Schintke)
• Lovebyte 2023 – 3rd place combined 32 byte demo (with Matthias Koch)

Teaching

• ProInformatik VII: Einstieg in die C-Programmierung (spring 2018, FU Berlin, German)
• ProInformatik VII: Einstieg in die C-Programmierung (summer 2018, FU Berlin, German)
• ProInformatik VII: Einstieg in die C-Programmierung (spring 2019, FU Berlin, German)
• Pattern-Datenbanken für heuristische Suchverfahren (spring 2019, HU Berlin, German)
  • slide deck on PDB construction (English)
• Objektorientierte Programmierung 3.1 – Programmierung in C (spring 2024, FU Berlin, German)
• Parallele Systeme (summer 2024, HTW Berlin, German)
• Objektorientierte Programmierung 3.1 – Programmierung in C (spring 2025, FU Berlin, German)
• Objektorientierte Programmierung 3.1 – Programmierung in C (spring 2026, FU Berlin, German)
• Systemverwaltung – Softwarepaketierung auf FreeBSD (spring 2026, FU Berlin, German)

Mentoring

• Google Summer of Code 2024 Port amd64 SIMD libc optimizations to aarch64 (FreeBSD, with Ed Maste)
• Google Summer of Code 2024 Port amd64 SIMD libc optimizations to riscv64 (FreeBSD, with Ed Maste)
• Google Summer of Code 2025 Full Disk Administration Tool for FreeBSD (FreeBSD, with Alfonso Siciliano)
• Google Summer of Code 2026 Enhancing Zoned Storage Support on FreeBSD (FreeBSD, with Alan Somers and Ken Merry)

Links

• Berlin Linux User Group
• c-base
• Stack Overflow profile
• github profile
• curriculum vitæ