Re: [Boost-users] Meta Template Programming with MPL - Compiler Bug or is the code really so evil slow?

From: evilissimo (evilissimo_at_[hidden])
Date: 2006-02-20 05:12:18

Hey Aleksey,

Thank you for the answer. James already said that before and we've 
figured out that it would take many days to finish the compilation. ;)
Fortunately this was only an experimental test after reading a few 
chapters of your ( and Davids) book, I've just buyed.
I am really interessted in this kind of programming, at least in theory 
until I know if I could use this once in some code.

I appreciate the excersises in the book since they help me to dig into 
the subject with some practice. It is sometimes hard to figure out own 
excercises for such a topic *g*.

Thanks for such a good book about this topic. I really like it :)

BR
Vinzenz

Aleksey Gurtovoy schrieb:
> Vinzenz 'evilissimo' Feenstra writes:
>   
>> I've written a little Meta Template Program which should calculate the
>> first 3 perfect numbers. ( range 1 - 500 )
>>
>> The code is compilable if you use the range 1 - 30 really fast and
>> works correctly. But I've tried to compile the code but I can't get it
>> finished.
>>
>> Someone tried it on a Machine with 40 GB RAM and it now compiles for
>> more than 12 hours and uses more than 7.1 GB RAM ( the compilation )
>>
>> I've tried it by myself with g++ 3.4.x and g++ 4.0.x and with VC++ 7.1
>>
>> The code works on all tested compilers if the range would be 1 - 30 but
>> If the range is 1 - 500 VC++ says:
>>
>> d:\boost\vc71\include\boost-1_33_1\boost\mpl\aux_\preprocessed\plain\apply_wrap.hpp(48):
>> fatal error C1204: compiler limit: internal structure overflow.
>>
>> ( This seems to be a known bug in VC++
>> http://support.microsoft.com/default.aspx?scid=kb;en-us;883655 )
>>
>> and g++ compiles and compiles and uses more and more RAM.
>>
>> Is the code really so evil slow or is it a compiler Bug in g++?
>>     
>
> The former: your algorithm is basically O(n^2). For n=500, that's a
> lot of work for the compiler.
>
>