""" Continuing with the previous example of “ß”, one has lowercase("ss") != lowercase("ß") but uppercase("ss") == uppercase("ß"). Conversely, for legacy reasons (compatibility with encodings predating Unicode), there exists a Kelvin sign “K”, which is distinct from the Latin uppercase letter “K”, but also lowercases to the normal Latin lowercase letter “k”, so that uppercase("K") != uppercase("K") but lowercase("K") == lowercase("K").
The correct way is to use Unicode case folding, a form of normalization designed specifically for case-insensitive comparisons. Both casefold("ß") == casefold("ss") and casefold("K") == casefold("K") are true. Case folding usually yields the same result as lowercasing, but not always (e.g., “ß” lowercases to itself but case-folds to “ss”). """
One question I have is why have Kelvin sign that is distinct from Latin K and other indistinguishable symbols? To make quantified machine readable (oh, this is not a 100K license plate or money amount, but a temperature)? Or to make it easier for specialized software to display it in correct placed/units?
IMO the confusing bit is giving it a lower case. It is a symbol that happens to look like an upper case, not an actual letter…
gb18030.ucm
ibm-1364_P110-2007.ucm
ibm-1390_P110-2003.ucm
ibm-1399_P110-2003.ucm
ibm-16684_P110-2003.ucm
ibm-933_P110-1995.ucm
ibm-949_P110-1999.ucm
ibm-949_P11A-1999.ucmHowever, those symbols doesn't have lower case variants. Moreover, lower case k means kilo-, not a «smaller Kelvin».
But, I dunno. Why would anybody apply upper or lower case operators to a temperature measurement? It just seems like a nonsense thing to do.
Unicode has the goal of being a 1:1 mapping for all other character encodings. Usually weird things like this is so there can be a 1:1 reversible mapping to some ancient character encoding.
I grouped all Unicode 17 case-folding rules and built ~3K lines of AVX-512 kernels around them to enable fully standards-compliant, case-insensitive substring search across the entire 1M+ Unicode range, operating directly on UTF-8 bytes. In practice, this is often ~50× faster than ICU, and also less wrong than most tools people rely on today—from grep-style utilities to products like Google Docs, Microsoft Excel, and VS Code.
StringZilla v4.5 is available for C99, C++11, Python 3, Rust, Swift, Go, and JavaScript. The article covers the algorithmic tradeoffs, benchmarks across 20+ Wikipedia dumps in different languages, and quick starts for each binding.
Thanks to everyone for feature requests and bug reports. I'll do my best to port this to Arm as well — but first, I'm trying to ship one more thing before year's end.
But why are you using the case-folding rules and not the collation rules?
do the go bindings require cgo?
Thanks for the work you do
There's only two "easy" solutions I can see: switch to N:N threading model or make the C code goroutine-aware. The former would speed up C calls at the expense of slowing down lots of ordinary Go code. Personally, I can still see some scenarios where that's beneficial, but it's pretty niche. The latter would greatly complicate the use of cgo, and defeat one of its core purposes, namely having access to large hard-to-translate C codebases without requiring extensive modifications of them.
A lot of people compare Go's FFI overhead to that of other natively compiled languages, like Zig or Rust, or to managed runtime languages like Java (JVM) or C# (.NET), but those alternatives don't use green threads (the general concept behind goroutines) as extensively. If you really want to compare apples-to-apples, you should compare against Erlang (BEAM). As far as I can tell, Erlang NIFs [1] are broadly similar to purego [2] calls, and their runtime performance [3] has more or less the same issues as CGo [4].
[1]: https://www.erlang.org/doc/system/nif.html
[2]: https://pkg.go.dev/github.com/ebitengine/purego
[3]: https://erlang.org/documentation/doc-10.1/doc/efficiency_gui...
[4]: https://www.reddit.com/r/golang/comments/12nt2le/when_dealin...
However, the "normal" execution model on all of them is using heavyweight native threads, not green threads. As far as I can tell, FFI is either unsupported entirely or has the same kind of overhead as Go and Erlang do, when used from those languages' green threads.
My impression is that the go ffi is with big overhead because of the specific choices made to not care about ffi because it would benefit the go code more?
My point was that there's other gc languages/envorionments that have good ffi and were somehow able all these decades to create scalable multithreaded applications.
Both Java and Rust flirted with green threads in their early days. Java abandoned them because the hardware wasn't ready yet, and Rust abandoned them because they require a heavyweight runtime that wasn't appropriate for many applications Rust was targeting. And yet, both languages (and others besides) ended up adding something like them in later anyway, albeit sitting beside, rather than replacing, the traditional N:N threading they primarily support.
Your question might just be misdirected; one could view it as operating systems, and not programming languages per se, that screwed it all up. Their threads, which were conservatively designed to be as compatible as possible with existing code, have too much overhead for many tasks. They were good enough for awhile, especially as multicore systems started to enter the scene, but their limitations became apparent after e.g. nginx could handle 10x the requests of Apache httpd on the same hardware. This gap would eventually be narrowed, to some extent, but it required a significant amount of rework in Apache.
If you can answer the question of why ThreadPoolExecutor exists in Java, then you are about halfway to answering the question about why M:N threading exists. The other half is mostly ergonomics; ThreadPoolExecutor is great for fanning out pieces of a single, subdividable task, but it isn't great for handling a perpetual stream of unrelated tasks that ebb and flow over time. EDIT: See the Project Loom proposal for green threads in Java today, which also brings up the ForkJoinPool, another approach to M:N threading: https://cr.openjdk.org/~rpressler/loom/Loom-Proposal.html
I was worried (I find it confusing when Unicode "shadows" of normal letters exist, and those are of course also dangerous in some cases when they can be mis-interpreted for the letter they look more or less exactly like) by the article's use of U+212A (Kelvin symbol) as sample text, so I had to look it up [1].
Anyway, according to Wikipedia the dedicated symbol should not be used:
However, this is a compatibility character provided for compatibility with legacy encodings. The Unicode standard recommends using U+004B K LATIN CAPITAL LETTER K instead; that is, a normal capital K.
That was comforting, to me. :)
Isn't this why Unicode normalization exists? This would let you compare Unicode letters and determine if they are canonically equivalent.
If you look in allkeys.txt (the base UCA data, used if you don't have language-specific stuff in your comparisons) for the two code points in question, you'll find:
004B ; [.2514.0020.0008] # LATIN CAPITAL LETTER K
212A ; [.2514.0020.0008] # KELVIN SIGN
Compare e.g. :
1D424 ; [.2514.0020.0005] # MATHEMATICAL BOLD SMALL K
Also, as shown in the later tables, the Armenian and Georgian fast paths still have room for improvement. Before introducing higher-level APIs, I need to tighten the existing Armenian kernel and add a dedicated one for Georgian. It’s not a true bicameral script, but some characters are folding fold targets for older scripts, which currently forces too many fallbacks to the serial path.
Interestingly enough this library doesn't provide grapheme cluster tokenization and/or boundary checking which is one of the most useful primitive for this.
If you’re in control of all data representations in your entire stack, then yes of course, but that’s hardly ever the case and different tradeoffs are made at different times (eg storage in UTF-8 because of efficiency, but in-memory representation in UTF-32 because of speed).
StringZilla added full Unicode case folding in an earlier release, and had a state-of-the-art exact case-sensitive substring search for years. However, doing a full fold of the entire haystack is significantly slower than the new case-insensitive search path.
The key point is that you don’t need to fully normalize the haystack to correctly answer most substring queries. The search algorithm can rule out the vast majority of positions using cheap, SIMD-friendly probes and only apply fold logic on a very small subset of candidates.
I go into the details in the “Ideation & Challenges in Substring Search” section of the article
Modern processors are generally computing stuff way faster than they can load and store bytes from main memory.
The code which does on the fly normalization only needs to normalize a small window. If you’re careful, you can even keep that window in registers, which have single CPU cycle access latency and ridiculously high throughput like 500GB/sec. Even if you have to store and reload, on-the-fly normalization is likely to handle tiny windows which fit in the in-core L1D cache. The access cost for L1D is like ~5 cycles of latency, and equally high throughput because many modern processors can load two 64-bytes vectors and store one vector each and every cycle.
First normalizing everything and then comparing normalized versions isn’t as fast.
And it also enables “stopping early” when a match has been found / not found, you may not actually have to convert everything.
You’re running the exact same code, but are more more efficient in terms of “I immediately use the data for comparison after converting it”, which means it’s likely either in a register or L1 cache already.
> ICU has many bindings. The Rust one doesn’t expose any substring search functionality, but the Python one does:
Python's ICU support is based on ICU4C. Rust's ICU "bindings" are actually a new implementation called ICU4X, by developers who worked on i18n at Mozilla and Google and on ICU4C, with the goal of a cleaner, more performant implementation that is also memory safe. Maybe not relevant (as in substantially altering the benchmarks), but it's at least worth noting that the ICU backends aren't consistent throughout.
Also very cool and approachable guy.
(Best wishes if you're reading this.)
Unicode avoids "different" and "same", https://www.unicode.org/reports/tr15/ uses phrases like compatibility equivalence.
The whole thing is complicated, because it actually is complicated in the real world. You can spell the name of Gießen "Giessen" and most Germans consider it correct even if not ideal, but spelling Massachusetts "Maßachusetts" is plainly wrong in German text. The relationship between ß and ss isn't symmetric. Unicode captures that complexity, when you get into the fine details.
Which is why we also have to deal with the ue, ae, oe kind of trick, also known as Ersatzschreibweise.
Then German language users from de-CH region, consider Mass the correct way.
Yeah, localization and internalization is a mess to get right.
In practice you can do pretty well with a universal approach, but it can’t be 100% correct.
However, it is likely that it has never been pronounced "sz", but always "ss" and the habit of writing "sz" for the double consonant may have had the same reason as the writing of "ck" instead of the double "kk".
Maß capitalized (used to be) MASS.
Funnily enough, Mass means one liter beer (think Oktoberfest).