[fpc-devel] TList slowness in classes

[Michael Van Canneyt]

On Fri, 24 Dec 2004, Michalis Kamburelis wrote:

> Hi,
>
> I tested your code and found that indeed version in ucopylist is
> slightly faster (by about 9.5 / 7 =~ 1.357). Two things:
>
> 1. Speedup is only 1.357x, not 3x, like you said. Are you sure that
> you're getting 3x speedup ? On what OS and with what FPC version are you
> testing this ? I was doing tests with Linux/i386 with FPC 1.9.4 and
> 1.9.5 (from CVS 2004-12-20).
>
> 2. Still, speedup 1.357x may be significant in some cases so I
> investigated what's the cause:
>
> After many tests I found that this slight speedup is caused by the fact
> that in ucopylist you declared string constants SListIndexError,
> SListCapacityError and SListCountError as normal constants while with
> original Classes unit these constants are taken from RTLConst unit that
> defines them as resourcestrings.
>
> Using resourcestrings in RTL is a must, since this allows to translate
> error messages without modifying unit Classes sources.
>
> However in this case exceptions are not raised, so resourcestrings are
> not actually used. But it looks that any procedure that uses some
> resourcestring in implementation is doomed to be slower than the similar
> procedure that instead uses normal string consts, *even if this
> procedure doesn't actually access the string at runtime*. It seems that
> if some procedure uses resourcestring then upon entry it does some
> lengthy initialization of this resourcestring, even if it will not
> actually make use of that resourcestring.

This is because there is an extra (implicit) Try/Finally block.

Michael.