[patch] Preprocessorised tr1::tuple

[Paolo Carlini]

Hi Chris,

[snip]

Thanks for the interesting details... I hope to discuss some later...

> One thing I don't know a lot about is the precompiled header support. 
> If by the time TR1 is considered stable and generally usable the 
> precompiled headers support is on by default, and is capable of 
> handling this unrolling macro monstrosity, then that might "fix" the 
> problem?

Well, I think so (By the way, I think we should work on documenting PCHs 
usage... Myabe Jonathan want to tackle this?!? ;)

Anyway, why don't you do some experiments yourself?!? Basically you just 
have to create a *.h file which includes the relevant tr1 headers and 
nothing else. Say you call it "tr1_headers.h". Then you compile it and 
end up with "tr1_headers.h.gch". Done! Then you can time how much it 
takes to compile any given user code (maybe starting with the empty 
one), including tr1_headers.h (if available, the precompiled version, 
"tr1_headers.h.gch", is automatically used in its place) instead of the 
tr1 headers directly. The overhead of loading from disk the big 
"tr1_headers.h.gch" discounted, probably the performance improvement is 
substantial and should benefit the new scheme much more than the old 
one! I would be curious to know the numbers...

Paolo.