Re: Vague question about lpeg performance

[Jerome Vuarand <jerome.vuarand@...>]

2010/4/2 Stefan <stefan@chehalispost.com>:
> Jerome Vuarand wrote:
>>
>> Hi list,
>>
>> I have an application that do intense use of JSON (a CouchDB view
>> server and client library). I started with JSON4Lua, which is pure Lua
>> but was way too slow for big structures. I switched to luajson, which
>> is based on lpeg, and achieved to do in milliseconds what JSON4Lua
>> sometimes took minutes to do.
>>
>> Now in my view server, for simple views and relatively big datasets
>> (so that the code is mostly dominated by JSON conversions), Lua is
>> approximately 10 to 20% faster than JavaScript (SpiderMonkey 1.7.0).
>>
>> So my question is, can I expect a significative performance
>> improvement by using a JSON parsing library written in pure C (that
>> would use the Lua C API for data structures construction) as opposed
>> to luajson lpeg parser that does the construction from Lua code ?
>>
>> Regards,
>>
>> Doub.
>>
>
> Perhaps a benchmark is in order?
>
> YAJL is reportedly among the fastest C JSON libs around. There is a Lua
> module for it here:
>
> http://github.com/brimworks/lua-yajl/
>
> A trivial bench between lua-yajl and json4lua encoding a small array 100,000
> times shows this:
>
> alpha# time lua-5.1 yajltest.lua
> 3.967u 0.000s 0:03.97 99.7%     177+983k 0+0io 0pf+0w
>
> alpha# time lua-5.1 jsontest.lua
> 9.170u 0.000s 0:09.17 100.0%    175+973k 0+0io 0pf+0w
>
> 230% faster is what I am seeing - YMMV

Thanks for the tip. lua-yajl decoding seems to be about 18% faster
than luajson, and encoding is 400% faster. But it seems to be a work
in progress, and it's less complete than luajson, so I guess I won't
switch just now.