1BRC--Nerd Sniping the Java Community

Your mission, should you decide to accept it, is the following: aggregate temperature values from a CSV file and group them by weather station name. There’s only one caveat: the file has one 1,000,000,000 rows!

This is the task of the “One Billion Row Challenge” which went viral within the Java community earlier this year. Come and join me for this talk where I’ll dive into some of the tricks employed by the fastest solutions for processing the challenge’s 13 GB input file within less than two seconds. Parallelization and efficient memory access, optimized parsing routines using SIMD and SWAR, as well as custom map implementations are just some of the topics which we are going to discuss.

I will also share some of the personal experiences and learnings which I made while running this challenge for and with the community.

Transcript

5. #1BRC | @gunnarmorling Today’s Mission Learn About…
6. #1BRC | @gunnarmorling • Software engineer at Decodable • Former project lead of Debezium • kcctl 🧸, JfrUnit, ModiTect, MapStruct • Java Champion • 1⃣ 🐝 🏎 Gunnar Morling
8. #1BRC | @gunnarmorling The Goals Learn something new Have some fun along the way Inspire others to do the same
9. #1BRC | @gunnarmorling The Rules • Java-only; Version of your choice • No dependencies • No caching • 10K stations, -99.9°C - +99.9°C • Copying allowed
10. #1BRC | @gunnarmorling Evaluation Environment • 32 core AMD EPYC™ 7502P (Zen2), 8 Cores used • 128 GB RAM • File on RAM disk • Five runs, slowest and fastest discarded Image © Joe Haupt https://flic.kr/p/2mG3vWA (CC BY-SA 2.0)
11. #1BRC | @gunnarmorling Baseline ⌛ 04:49.679
12. Parallelization Ozzy Delaney https://flic.kr/p/pMsvzE (CC BY-SA 2.0 DEED)
13. #1BRC | @gunnarmorling Parallelization ⌛ 71 sec.
14. #1BRC | @gunnarmorling JEP 454 Foreign Function & Memory API https://openjdk.org/jeps/454 Introduce an API by which Java programs can interoperate with code and data outside of the Java runtime. By efficiently invoking foreign functions (i.e., code outside the JVM), and by safely accessing foreign memory (i.e., memory not managed by the JVM), the API enables Java programs to call native libraries and process native data without the brittleness and danger of JNI.
15. #1BRC | @gunnarmorling Parallelization–Chunking the File We have many cores, let’s put them to use!
16. #1BRC | @gunnarmorling Parallelization–Chunking the File
17. Parsing jjmusgrove https://flic.kr/p/2mJbA8S (CC BY 2.0 DEED)
18. #1BRC | @gunnarmorling Parsing – Byte by Byte
19. #1BRC | @gunnarmorling Parsing – Byte by Byte ⌛ 20 sec.
20. #1BRC | @gunnarmorling Parsing – SWAR SIMD Within a Register
21. #1BRC | @gunnarmorling Parsing Branchless Programming https://en.wikipedia.org/wiki/Branch_predictor
22. #1BRC | @gunnarmorling Parsing – SWAR SIMD Within a Register https://richardstartin.github.io/posts/finding-bytes
23. #1BRC | @gunnarmorling Parsing – SIMD Single Instruction, Multiple Data https://speakerdeck.com/gunnarmorling/to-the-moon-and-beyond-with-java-17-apis
24. Bookkeeping R. D. Barry https://flic.kr/p/P5RWWR (CC BY-SA 2.0 DEED)
25. #1BRC | @gunnarmorling Custom Maps – Linear Probing
26. #1BRC | @gunnarmorling Custom Maps – Hash Collisions!
27. #1BRC | @gunnarmorling Further Tricks & Techniques • GraalVM as JIT Compiler • GraalVM native binary • The “spawn trick” • Unsafe • EpsilonGC • Super-scalar execution
28. #1BRC | @gunnarmorling Parsing Perfect Hashing • Can’t use perfect hashing for keys… but for values! • Only 1,999 distinct values: -99.9, -99.8, ..., 0.0, ..., 99.8, 99.9
29. The Results Clint Budd https://flic.kr/p/2m6F7hw (CC BY 2.0 DEED)
30. #1BRC | @gunnarmorling Results
31. #1BRC | @gunnarmorling Results – 32 Cores / 64 Threads
32. #1BRC | @gunnarmorling Results – 10K Key Set
33. #1BRC | @gunnarmorling It’s a Long Journey
34. #1BRC | @gunnarmorling Should You Do Any of This? It Depends
35. #1BRC | @gunnarmorling The Hardest Earned Coffee Mug…
36. #1BRC | @gunnarmorling Lessons Learned
37. #1BRC | @gunnarmorling Lessons Learned • Precise rules, covering corner cases • Automate, automate, automate • Build a community • Use dedicated hardware
38. #1BRC | @gunnarmorling Lessons Learned
39. #1BRC | @gunnarmorling The 1BRC Community • TCK • Environment • Evaluation Scripts
40. #1BRC | @gunnarmorling 1BRC Mythbusters
41. #1BRC | @gunnarmorling What’s Next? ?
42. #1BRC | @gunnarmorling • Repository https://github.com/gunnarmorling/1brc/ • Show & Tell https://github.com/gunnarmorling/1brc/ discussions/categories/show-and-tell • The Billion Row Challenge–Step-by-step from 71s to 1.7s https://questdb.io/blog/billion-row-challenge-step-by-step/ Learn More
43. #1BRC | @gunnarmorling Resources Relevant JEPs and more • Vector API (Incubator): https://openjdk.org/jeps/469 • Foreign Function and Memory API: https://openjdk.org/jeps/454 • CRaC: https://openjdk.org/projects/crac/
44. #1BRC | @gunnarmorling Resources Hacker’s Delight
45. #1BRC | @gunnarmorling gunnar@decodable.co @gunnarmorling 📧 Thank You! Q & A