Re: Reading and writing a big file in Ada (GNAT) on Windows XP

["Jeffrey R. Carter" <jrcarter@acm.org>]

Fionn Mac Cumhaill wrote:
> 
> All it does is read lines in a loop from a text file with
> Ada.Text_IO.Get_Line, does minor modifications on about 80% of the
> lines that it reads, and writes the lines to an output file with
> Put_Line. 
> 
> 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.
> 
> The problem is that the input file has more than 10 million lines of
> text in it. The program works perfectly, but takes about 5 hours to
> run. The Cygwin version of wc can count the lines in the input file in
> less than one minute.
> 
> Why is this so slow? 
> Do I have an Ada problem, a GNAT problem, or a MinGW problem?

It's hard to tell. Text_IO is quite heavy-weight compared to C text I/O, 
but I'd be surprised if it made that much difference.

This sounds as if it would be a pretty simple program; if so, you could 
post it (or a reasonable facsimile, if there's a reason you can't post 
the actual code) here, and we would be better able to help.

-- 
Jeff Carter
"Nobody expects the Spanish Inquisition!"
Monty Python's Flying Circus
22