Re: Vague question about lpeg performance

[Stefan <stefan@...>]

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

--

Stefan