Re: Ada Shootout program for K-Nucleotide (patches)

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Georg Bauhaus wrote on comp.lang.ada:
> This is about the K-Nucleotide program at the
> Computer Language Benchmark Game,http://shootout.alioth.debian.org/u32/benchmark.php?test=knucleotide&...
> where some Ada programs have started to fail.
>
> In order to have one of them work again, I have patched
> knucleotide.gnat, with some success.  New version is here:http://home.arcor.de/bauhaus/Ada/knucleotide.gnat
>
> Comments?  Does it work on your machine?
>
> The two changes:
>
> 1 - [stack exhaustion] a loop reading input lines into an
>  ubounded  string replaces the recursive String "&"ing
>  procedure. (Noting that the input text file is ~240MB ...)
>
> 2 - [heavy bounded strings] a lightweight bounded string ADT
>  replaces an instance of Generic_Bounded_Length, yielding
>  an improved running time of ~22s down from ~30s for
>  the 2,500,000 case.
>
> Still, on a relatively small virtual machine running 64bit
> Debian, the program cannot handle the 25,000,000 case.

I note that both Martin and yourself use Ada.Text_IO (especially
Read_Line) which is notoriously slow.  I would use Character'Read and
a finite state machine to detect the portion of the input file to be
processed, then to fill in the buffer.  That should be faster.

(the shootout rules state that the program must read "line by line"
but that does not make sense since Unix has no concept of a line and
all programs must therefore read and parse each byte to detect ends of
lines).

--
Ludovic Brenta (too busy to help any further, alas).