Re: [Tracker] some patches

[Jamie McCracken <jamiemcc blueyonder co uk>]

On Thu, 2008-02-14 at 17:31 +0100, Laurent Aguerreche wrote:
> Le mercredi 13 fÃvrier 2008 Ã 18:09 +0100, Carlos Garnacho a Ãcrit :
> > Hi!,
> >
> > This was just a heads up to these three bugs:
> >
> > #513692 : This one just packs booleans in guints, so it should improve
> > size in most used structs.
>
> Is it so interesting to save some bytes this way?
>
> In tracker-utils, this patch will replace 25 gbooleans with 25 "uint:1".
> If I assume that gboolean is a typedef of gint and that gint uses 4
> bytes, this patch will save (25*4)-25 = 75 bytes (perhaps a little bit
> more but IMHO not much more because we use pointers everywhere and we
> take care of memory allocations).
> So we would prefer to write some weird things (using of unsigned int
> instead of booleans) to save ~75 bytes?
>
> Another question: why glib does use a typedef of gint instead of a
> typedef of "guint:1" for its booleans?


the 25 booleans will be packed into a single gint of 32 bytes 

a single boolean may use 32 bits on a 32 bit machine although that will
depend on cpu architecture of course (just guessing the risc based arm
chip on the nokia works like that?)

> > #513691 : a similar improvement to #511788 (already committed) in a
> > different function.
>
> +     res = g_ptr_array_sized_new (100);
>
> What is "100"?!

array has preallocated for 100 entries (or rows in the dataset I believe)

at least that is my understanding, carlos can correct me if im wrong

jamie