[antlr-interest] ANTLR performance

[Jim Idle]

Jan Obdržálek wrote:
> Hello,
>
> for our student research project we implemented a C grammar in ANTLR
> 3.1. (The grammar fully implements ANSI C99, and mostly implements the
> GNU C extensions - the notable exception being the attributes, which
> are a real pain.) However we found the performance of the parser to be
> a bit lacking. We therefore ran some tests. In addition to the default
> Java target, we modified the grammar for the C target. The results
> were then compared to the results obtained by using the GNU C
> compiler. This is a fair comparison, since gcc also uses a  top-down
> recursive parser (although hand-coded). Actually the test is tougher
> on gcc, since gcc does full compilation, compared to just building the
> AST in the case of ANTLR.
>
> The results can be summarized as follows (more details about the test
> at the end of this post):
>
>  - ANTLR/Java is obviously the slowest one [and there is a serious
> start-up/close-down overhead]
>  - ANTLR/C is faster, but still miles behind the gcc
Looking at your gprof file, it claims that the function call 
setCharPositionInLine() is called 4 times and takes 0.67 seconds, 
however this function is just this:

static  void        setCharPositionInLine    (pANTLR3_COMMON_TOKEN 
token, ANTLR3_INT32 pos)
{
    token->charPosition = pos;
}

So, I am having a hard time buying that. Try kcachegrind and see if this 
gives a different perspective, but as I say, we need to see the grammar 
really. I also suggest trying the beta 3.1.2 runtime which is in 
perforce/fisheye, though this probably means you need to use a current 
build of the ANTLR tool, which you can get from hudson: 
www.antlr.org/hudson.

Jim