Re: Excessively inefficient source code modifications

On 11 February 2010 09:26, Jesús Díaz Vico <[email protected]> wrote:
> Hello,
>
> I've made some changes in the libvorbis-1.2.3 source code to introduce
> some functionality I need for a project I'm working on. For compilation,
> besides including some macro definitions I need to pass to the C
> preprocessor, and linking with the math library somewhere (and including
> the source files I've implemented, of course) I've made no big changes
> in the Makefile or configure scripts. But when I run my modified oggenc
> program, the execution time becames excessive (for coding 2 secs of
> audio it spents approximately 2 mins, with default parameters). The
> modifications I've made consist basically in some extra computation
> involving the residual vectors (so it executes once for each residue
> vector). I've measured independently the average time for the whole
> extra code and it takes approximately 0.00012 secs per call (so that
> would make roughly 0.00012*channels*frames extra encoding time for an
> audio file). Despite I've re-re-rechecked my code and I haven't found
> anything strange, I don't discard at all that may be there are some
> algorithmic errors left that may make my code be a bit inefficient, but
> making 2 secs go to 2 mins is quite alarming and far away from
> permissible. Supposing I have no important algorithmic errors, could
> this excessive overload be caused by a compiling issue? (that wouldn't
> surprise me, as my knowledge about autoconf/automake/make scripts is
> quite basic...).
>
> I'd just like to discard the fact of having a compilation issue before
> starting another intensive and detailed analysis of the code. If after
> another bunch of extra hours and thousands of code lines rechecked, I
> find that it was a compilation issue, I might be forced to make a
> pilgrimage to the Himalayas to find myself or something... ;)

what platform and compiler are you using, and can you post your
changes somewhere as a patch (both code and build changes).

Conrad.