On Thursday, January 2, 2014 6:47:58 PM UTC+1, Nicolas Pierron wrote:
> On 01/02/2014 07:31 AM, Nicolas B. Pierron wrote:
>
> I should have wrote that with a past tense …
>
> https://github.com/jviereck/regexp.js
So far I hadn't done any performance numbers for RegExp.JS. I looked into this
and thanks to the help of Till I got the Octane benchmark running in the JS
shell [1].
Before converting the entire Octane RegExp benchmark to run using RegExp.JS I
thought I just try the first RegExp tested in the benchmark. This means the in
terms of code changes:
diff --git a/regexp.js b/regexp.js
- var re0 = /^ba/;
+ var re0 = new RegExpJS(/^ba/);
Just changing this one RegExp caused the score from ~1480 on my machine to drop
to 77 (!!!) using the RegExp.JS library (& my.mood = :( ).
Okay, so maybe RegExp.JS is doing something completely wrong, which is why I
tried another dump approach and defined:
function RegExpJS(reg) { }
RegExpJS.prototype.exec = function(str) {
if (str.startsWith('ba')) {
return ['ba'];
} else {
return null;
}
}
This RegExpJS object ONLY works HARDCODED with the first regexp of the octane
benchmark (/^ba/) - cheating, I know, but let's see where this gets us in terms
of performance. Running the regexp.js benchmark with this RegExpJS definition
and the modification |var re0 = new RegExpJS(/^ba/);| resulted in a score of
~1340. Better than 77, but still a huge drop compared to 1480 by only changing
one RegExp in the benchmark!
(If you wonder if replacing the |if(str.startsWith('ba'))| call with |if
(str[0] == 'b' && str[1] == 'a') {| --- no, that doesn't make any difference in
terms of performance :/).
---
Without knowing anything about the Spidermonkey JS internals, this very small
benchmarking raises the following questions to me:
1) Is the YARR implementation so much faster than anything written in plane JS
(even if the JS is highly optimized for the RegExp and matches the string in
the best optimial way)?
2) Is there a performance bug in Spidermonkey, that makes even the plain
RegExpJS running only /^ba/ such slow?
Cheers,
- Julian
[1] Using the js shell provided at
http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk/ dated on
the 04-Jan-2014 11:50.
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