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.
Thank you and Peter for answers. This way I was able to see how try...finally section looks in assembler :) Anyway, I understand that the answer is "can't be speed up". OK, I can live with that.
-- Michalis
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