Let's stop parser Hell

[Dmitry Olshansky]

On 06-Jul-12 00:16, Roman D. Boiko wrote:
>> isKeyword_Dummy (baseline): 2738 [microsec] total, 50 [ns / lookup].
> This one calculates a sum of all identifier code units. Included for
> comparison.
>
>> isKeyword_Dictionary: 4247 [microsec] total, 242 [ns / lookup].
> Check whether an identifier is a keyword using AA (dictionary) lookup.
>
>> isKeyword_SwitchByLengthThenByChar: 1593 [microsec] total, 91 [ns /
>> lookup].
> Switch by identifier length at the top, then recursively switch by each
> character. Clearly a winner, but I think it can be improved further.
>
I'd stress the fact that it's a fully unrolled & hard-coded
switch that takes a lot of pages (~72Kbytes). It's easily be perfect.
Sorry, couldn't resist ;)
And I'm not sure how much it could be optimized maybe some measly 10-30%.

>> Total: 104183 identifiers + 17488 keywords.
> Analyzed the largest Phobos file (DateTime? I didn't check the name.)
> Results are consistent for other files, too.
It is std.datetime as I've been running this benchmark against it and 
seen the same numbers :)

-- 
Dmitry Olshansky