Re: 'Base

[Martin Krischik <krischik@users.sourceforge.net>]

Per Sandberg wrote:

> Ole-Hjalmar Kristensen wrote:
>> My gut reaction was also that Ada will always outperform Java, but I
>> have found at least one case there this is not true.  I recently wrote
>> a simple test program to transpose a two-dimensional array in Java,
>> Ada, C++, and C. The purpose was not really to compare languages, but
>> to see the effects of caching. There were two different alogrithms
>> used, one a simple nested loop, the other a recursive subdivision with
>> a nested loop at the lowest level. When the simple nested loop was
>> tested with large data sets (~ available RAM on the machines) the
>> diffence between Ada, C, and C++ was insignificant, all being 3-4
>> times faster than Java. However, when testing the recursive version, I
>> found that Java was actually about 10% faster than the other three,
>> which again came extremely close to each other. Apparently the JIT
>> compiler had plenty of time to do its work and come up with pretty
>> optimal code. The other interesting result from the experiment was
>> that the recursive  version was from 3-4 to 20 times faster than the
>> simple nested loop.
>> 
>> 
>> 
>>>>>>>"MK" == Martin Krischik <krischik@users.sourceforge.net> writes:
>> 
>> <snip>
>>     MK> Ada arrays are not a primitive type - they are a quite complex
>>     and powerfull MK> type.
>> 
>>     MK> Performace? Ada allways outperform Java for a start. But Ada's
>>     build in MK> checks will also outperform C/C++ when used with all
>>     appropriate MK> "assert()"s in place.
>> 
>> <snip>
> 
> This is intresting but i have tried Ada (GNAT/GCC) with different
> optimisation levels and different validity checking.
> and fount that ther is a clearly visible diference in performance
> depending on how far the compiler is allowed to go in terms of
> optimisation. I have not done any qualified measurments but the guts
> feeling is that the performace may change bye a factor of at least 2
> depending on compiler switches.
> Also worth to mention that as far as i have seen ther is normaly areound
> 30% difference in performace when going from "-O0" to "-Os".

Sure - if you switch checks off and optimization on the program will be
faster.

If you compare Ada - with checks - with C/C++ - with assert then Ada will
have more change in optimization of those checks then C/C++ has on the
asserts.

Ada:

type X is range ...

f (Value : X) is ....

for I in X'Range loop
  f (i);
end loop;

C:

typedef int X;

extern f (X Value)
  {
  assert (Value >= X_First && Value <= X_Last)

  .....
  }

for (i= X_First ; X <= X_Last; i++)
  {
  f (i);
  }

Ada will make no checks at all while in C must check "Value" with each loop.

Remember: we live in a complex world and f () will be called a different
places - some where static analysis may prove the correctness of t the
parameter - like the example above - and some where it cant. Just removing
the assert is not an option.

Martin
-- 
mailto://krischik@users.sourceforge.net
Ada programming at: http://ada.krischik.com