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Date: Wed, 02 Sep 2009 10:44:01 +0200
From: Georg Bauhaus <rm.tsoh.plus-bug.bauhaus@maps.futureapps.de>
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Subject: Re: Ada Shootout program for K-Nucleotide (patches)
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Date: 2009-09-02T10:44:01+02:00
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Ole-Hjalmar Kristensen wrote:
>>>>>> "GB" == Georg Bauhaus <rm.dash-bauhaus@futureapps.de> writes:
> 
> I think the problem is not the explicit copy which happens when we hit
> the end of the buffer (easily verified, just increase the buffer size
> 10 times, the copying will happen 1/10 of the time, but execution time
> stays the same), but the implicit copy which seems to happen in the statement
> return In_Buf(Start..I-1); I do not know if this copy is unavoidable,
> or if the compiler could have optimized it away.

It looks like copying In_Buf(Start..I-1) be circumvented.
I have added a solution to Line_IO.

read() performance vs. Stream_IO.Read performance seems
to depend on the OS.  On a Mac here, read() is faster.
On Ubuntu, Stream_IO.Read is faster.

There is an issue with GNATs and End_File (GNATs other
than I guess the one you have). When comparing N <= 0,
``operator for type "System.Crtl.size_t" is not
directly visible''.  To work around this, I wrote

   function End_File return Boolean is
      type Size_T is mod 2**Standard'Address_Size;
      N0 : constant Size_T := Size_T(N);
      Zero : constant Size_T := 0;
   begin
      return N0 <= Zero;
   end End_File;

Finally, I think Get_Line_Test can be made more portable among Unix
compilers by changing GNAT specific Interfaces.C_Streams
into Interfaces.C; Could be slightly less convenient to
write, though?