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Re: About C++ and flex
From: |
Laurent Mascherpa |
Subject: |
Re: About C++ and flex |
Date: |
Thu, 22 Nov 2001 21:03:26 +0100 |
> >Did you ever experience weird performance issues with C++? I know
> >Laurent had disastrous performances which suddenly vanished when he
> >stopped using -+. Maybe he recalls what the problem was.
>
> I would not notice it, as the C++/Flex/Bison input codes I use are small,
> which I test on short inputs (not large computer PL input files and the
> like).
>
> I think though that early C++ compilers were not so efficient, so that
> might have produced slow code relative C. If that was the problem, more
> recent C++ compilers should not have it.
When input codes where small there was no visible speed problem. But
compared to parser produced without -+, with the exact same rules, it
was really much slower, especially on larger input codes (> 200 lines).
I did not take time to find why, but directly switched to /classical/
way of using Flex.
It was not so old, less than a year, I don't think it could have been
a problem of GCC. It could have been a problem of my scanner rules,
maybe exploiting a performance problem.
Laurent,