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Date: Sat, 28 Apr 2007 14:28:56 -0400
From: Jeffrey Creem <jeff@thecreems.com>
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Subject: Re: Reading and writing a big file in Ada (GNAT) on Windows XP
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Date: 2007-04-28T14:28:56-04:00
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Simon Wright wrote:
> Fionn Mac Cumhaill <invisible@hiding.from.spam> writes:
> 
>> The modifications consist of replacing a slice of text at the end of
>> a line with another bit of text. The biggest slice is 10 characters,
>> and the replacement slice is always smaller than the original
>> slice. An occasional line of text is about 6000 characters long, but
>> most are about 700 haracters.  Get_Line reads them into a String
>> variable that is 10,000 characters long.
> 
> Yesterday I found a performance (and stack!) related problem in GNAT's
> Ada.Strings.Fixed.Index. The string is mapped onto the stack before
> the search is done. But I wouldn't have thought this would result in a
> 5 hour run time. How do you decide which lines need conversion?

I agree, it does not seem that either that or the guesses I had related 
to zeroing at the string (a common mistake) would result in the level of 
slowdown being seen...However, now that you mention it, I see a few ugly 
things like that related to Ada.Strings.Fixed. Did you submit a bug 
report to FSF GCC?


As for the original poster, any chance you are doing dynamic memory 
allocation and leaking and perhaps causing swapping?