Russ Cox
Software engineer and a long-time technical lead of the Go programming language; author of plan9port and of the research.swtch.com essays.
Russ Cox did not write this page. ppll compiled it from their own words, each linked to the source. Is this you? · Report a mistake
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What they believe
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Floating-point printing and parsing algorithms are converging toward an optimal solution.
Given the simplicity and speed of the algorithms in this post and the increasingly small deltas between successive algorithms, perhaps we are nearing an optimal solution.
research.swtch.comSaid 19 Jan 2026This on korrents
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Comparing code coverage between passing and failing test runs is a cheap, effective way to localize a bug quickly.
Differential coverage is cheap to compute and display, and when it's right, it can save a lot of time.
research.swtch.comSaid 25 Apr 2025This on korrents
The bold line is korrents’ wording; the quote is theirs. These 2: what they wrote before what they said aloud, one per source, newest first.
Feed
As its own page →Hiding
8 October
26 September
19 August
10 July
27 February
19 January
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korrents.com
Floating-point printing and parsing algorithms are converging toward an optimal solution.Their words
Given the simplicity and speed of the algorithms in this post and the increasingly small deltas between successive algorithms, perhaps we are nearing an optimal solution.
10 January
19 December 2025
16 September 2025
29 August 2025
5 August 2025
28 May 2025
27 May 2025
25 April 2025
From one piece Differential Coverage for Debugging 2 beliefs · research.swtch.com
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korrents.com
Buggy code usually causes outright test failures rather than being silently exercised inside tests that still pass.Their words
a passing test can still execute buggy code if the bug is data-dependent, or if the test is not sensitive to the specific mistake in the code. But a lot of the time, buggy code only triggers failures.
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korrents.com
Comparing code coverage between passing and failing test runs is a cheap, effective way to localize a bug quickly.Their words
Differential coverage is cheap to compute and display, and when it's right, it can save a lot of time.
18 July 2024
From one piece Hash-Based Bisect Debugging in Compilers and Runtimes 2 beliefs · research.swtch.com
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Their words
One of the hardest things about debugging is running a program backward: there's a data structure with a bad value, or the control flow has zigged instead of zagged, and it's very difficult to understand how it could have gotten into that state.
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korrents.com
Writing a technique down, however basic it seems, is the first step to making it usable by everyone.Their words
But writing a trick down is the first step to making sure everyone can do it: magic tricks can be basic but not obvious.
2 April 2024
From one piece Timeline of the xz open source attack 2 beliefs · research.swtch.com
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korrents.com
The xz backdoor falls short of a Ken Thompson-style 'trusting trust' compromise, but comes a step closer to one.Their words
We're not at trusting trust levels yet, but it would be one step closer.
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Their words
It marks a watershed moment in open source supply chain security, for better or worse.
8 December 2023
5 December 2023
26 October 2023
18 August 2023
4 February 2023
23 January 2019
30 May 2018
Nothing matches.
Beliefs
Korrents What they believe 7 beliefs — each backed by an exact quote.
Each is a — compiled by korrents.com, not by them: the one-line wordings are korrents', the quotes are theirs.
Recent
Floating-point printing and parsing algorithms are converging toward an optimal solution.
Given the simplicity and speed of the algorithms in this post and the increasingly small deltas between successive algorithms, perhaps we are nearing an optimal solution.
Floating-Point Printing and Parsing Can Be Simple And Fast Said 19 Jan 2026
Comparing code coverage between passing and failing test runs is a cheap, effective way to localize a bug quickly.
Differential coverage is cheap to compute and display, and when it's right, it can save a lot of time.
Differential Coverage for Debugging Said 25 Apr 2025
Buggy code usually causes outright test failures rather than being silently exercised inside tests that still pass.
a passing test can still execute buggy code if the bug is data-dependent, or if the test is not sensitive to the specific mistake in the code. But a lot of the time, buggy code only triggers failures.
Differential Coverage for Debugging Said 25 Apr 2025
Show 4 more
Writing a technique down, however basic it seems, is the first step to making it usable by everyone.
But writing a trick down is the first step to making sure everyone can do it: magic tricks can be basic but not obvious.
Hash-Based Bisect Debugging in Compilers and Runtimes Said 18 Jul 2024
Debugging by reasoning backward from a bad state is inherently harder than reasoning forward from a known decision point.
One of the hardest things about debugging is running a program backward: there's a data structure with a bad value, or the control flow has zigged instead of zagged, and it's very difficult to understand how it could have gotten into that state.
Hash-Based Bisect Debugging in Compilers and Runtimes Said 18 Jul 2024
The xz backdoor marks a watershed moment in open source supply chain security.
It marks a watershed moment in open source supply chain security, for better or worse.
Timeline of the xz open source attack Said 2 Apr 2024
The xz backdoor falls short of a Ken Thompson-style 'trusting trust' compromise, but comes a step closer to one.
We're not at trusting trust levels yet, but it would be one step closer.
Timeline of the xz open source attack Said 2 Apr 2024
What is a korrent?
A korrent is a belief a person has stated in their own words: one sentence stating the claim, backed by a quote and a source, kept at korrents.com.
Under a name here, the quoted block is what they actually said. The korrent beneath it is the claim those words support, in korrents' wording — tap it to see the record, its source, and who else holds it.
Nobody here wrote their own korrents. They are compiled from public statements, and a person can change their mind, which is recorded too.
Recommends rcmnd
rcmnd What they recommend 5 things — each backed by an exact quote.
Compiled by rcmnd.app, not by them: the quotes are theirs, and each links to the post it was copied from.
Recent
Loved Fujitsu ScanSnap S510
More recent additions include an Apple Time Capsule for backing up the Mac and running the home network, a Netgear ReadyNAS Duo (with mirrored disks) for networked storage, and a Fujitsu ScanSnap S510.
usesthis.com 9 Apr 2011
Loved IBM ThinkPad X40
It was small, light, sturdy, and had three mouse buttons. What more could you want?
usesthis.com 9 Apr 2011
Loved Lenovo ThinkPad X201s
I recently replaced my X40 with a refurbished Lenovo Thinkpad X201s, which is also small, light, sturdy, and has three mouse buttons.
usesthis.com 9 Apr 2011
Show 2 more
Disliked Netgear ReadyNAS Duo
The only thing I might replace if I were starting over would be the ReadyNAS box.
usesthis.com 9 Apr 2011
Loved Samsung ML-1750 laser printer
The printer and the scanner both seemed extravagant at the time, but they have been absolute workhorses and well worth the money.
usesthis.com 9 Apr 2011
Where they publish
Blog research.swtch.com His essays on Go, software engineering and version control.
Recent
- Fast Unrounded Scaling: Proof by Ivy 19 Jan 2026 Proof that the fast unrounded scaling implementation is correct. (Floating Point Formatting, Part 4)
- Floating-Point Printing and Parsing Can Be Simple And Fast 19 Jan 2026 Fast and simple conversion between floating-point and decimal. (Floating Point Formatting, Part 3)
- Pulling a New Proof from Knuth’s Fixed-Point Printer 10 Jan 2026 A birthday proof for Don Knuth (Floating Point Formatting, Part 2)
Show 17 more
- Floating Point Formatting 10 Jan 2026
- Differential Coverage for Debugging 25 Apr 2025 Diffing code coverage for passing and failing runs can identify suspicious code blocks.
- Hash-Based Bisect Debugging in Compilers and Runtimes 18 Jul 2024 Binary search over program code or execution to find why a new library or compiler causes a failure.
- The xz attack shell script 2 Apr 2024 A detailed walkthrough of the xz attack shell script.
- Timeline of the xz open source attack 2 Apr 2024 A detailed timeline of the xz open source attack, from 2021 to 2024.
- Go Changes 8 Dec 2023 The way Go changes, and how to improve it with telemetry.
- Go Testing By Example 5 Dec 2023 The importance of testing, and twenty tips for writing good tests.
- Running the “Reflections on Trusting Trust” Compiler 26 Oct 2023 Ken Thompson’s Turing award lecture, running in your browser.
- C and C++ Prioritize Performance over Correctness 18 Aug 2023 The meaning of “undefined behavior” has changed significantly since its introduction in the 1980s.
- The Magic of Sampling, and its Limitations 4 Feb 2023 The magic of using small samples to learn about large data sets.
- Our Software Dependency Problem 23 Jan 2019 Download and run code from strangers on the internet. What could go wrong?
- What is Software Engineering? 30 May 2018 and what does Go mean by it? (Go & Versioning, Part 9)
- Go and Dogma 9 Jan 2017 Programming language dogmatics.
- A Tour of Acme 17 Sept 2012 A video introduction to Acme, the Plan 9 text editor
- Minimal Boolean Formulas 18 May 2011 Simplify equations with God
- Zip Files All The Way Down 18 Mar 2010 Did you think it was turtles?
- UTF-8: Bits, Bytes, and Benefits 5 Mar 2010 The reasons to switch to UTF-8
Link verified 5 Sept 2026. Recent items update automatically from the channel.
GitHub rsc His GitHub account.
Recent
- tmp — /tmp 8 Oct 2026
- cmd — Commands 26 Sept 2026
- agent — Agent helpers 19 Aug 2026
Show 8 more
- rf — A refactoring tool for Go 10 Jul 2026
- fpfmt — Floating-Point Printing and Parsing 27 Feb 2026
- github 19 Dec 2025
- nfs — Sun NFS 2.0 Release 16 Sept 2025
- gophershirt — Gopher Hawaiian Shirts 29 Aug 2025
- swtch — swtch.com web server 5 Aug 2025
- unix — Old Unix programs running on modern computers. 28 May 2025
- omap — Ordered map 27 May 2025
Link verified 5 Sept 2026. Recent items update automatically from the channel.
About the English under a post
Some people here publish in a language other than English. Where they do, this site shows a machine translation beneath the post, in this typeface — the site's own, not theirs.
The post itself is never changed, moved or hidden: what is set in the serif above is exactly what the person published, and it is what to quote them on. A translation can be wrong in ways that matter, especially about tone.
Only the post's own words are translated. A quoted post, a linked article and a belief on korrents.com are left in their original language.