Re: [boost] Excessive preprocessor_test compile times

From: Vesa Karvonen (vesa.karvonen_at_[hidden])
Date: 2001-12-19 04:33:43

From: "Jens Maurer" <Jens.Maurer_at_[hidden]>
> Vesa Karvonen wrote:
> > I'll see what can be done.
>
> I've checked in a change to status/compiler_status.html that
> has links to the compile times files, which I uploaded to the
> same place than the message files (sourceforge http).
>
> Please, all, have a look.

hmm... It seems that most compilers have a slow preprocessor. I guess I have
been lucky to use compilers that all have relatively fast preprocessors.

It IS possible to change the library implementation so that preprocessing time
is reduced. The downside is that more macros are needed. The current version
in the CVS uses the WHILE primitive to implement the arithmetic operations.
This way the macro recursion needs to be done only once. Previously ADD, SUB
and MUL were all implemented independently and preprocessing on some compilers
was clearly faster. The current implementation is significantly smaller, which
is why I think that it is preferable.

Reducing the length of macro names could also improve preprocessing times on
some compilers, but I think that it should not make much difference.

Another technique worth considering would be to use better algorithms (O(log
N) instead of O(N) or O(N*N)) to implement the arithmetic operations.
Previously I considered it waste of time, because I thought that the range
[0,128] was small enough so that the benefit would not be worth the effort.