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From: jonathan <johnscpg@googlemail.com>
Newsgroups: comp.lang.ada
Subject: Re: Tasking for Mandelbrot program
Date: Mon, 12 Oct 2009 15:46:38 -0700 (PDT)
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On Oct 12, 5:58=A0pm, Georg Bauhaus <rm.dash-bauh...@futureapps.de>
wrote:
> Lo and behold! =A0An Ada program is at #1 in two lists
> at the Shootout site. =A0Look for mandelbrot, the 64
> bit rankings. =A0Enjoy the moment while it lasts. :-)
>

Here is the address:

http://shootout.alioth.debian.org/u64q/benchmark.php?test=3Dmandelbrot&lang=
=3Dall

> The high speed is largely due to the new inner loop,
> composed by Jonathan Parker.

Well, I figured it out by reading the C program;) The C and C++
programs use INTEL sse2 intrinsics to get the best
performance out of the sse2 floating point units.
The INTEL sse2 intrinsics are IIUC a convenient interface
to intel sse2 assembly language:
http://msdn.microsoft.com/en-us/library/kcwz153a(VS.71).aspx

The result we can be proud of is the finding that GNAT/gcc
is just smart enough to produce optimal code without the
use of INTEL sse2 intrinsics, at least on the 64 bit machine.
The key to getting the best performance out of
the SSE hardware was presenting it
with 2 identical streams of instructions, each of which
starts with different initial conditions. It can
be done in high-level language as well as
the sse2 intrinsics.

The challenge in this part of the shootout was
non-trivial:  to get the mandelbrot calculation to
exploit all 4 cores of the test machine in parallel, (a
load-balancing/distributed-processing problem I mentioned
earlier in this thread) and to simultaneously put the
SSE floating point units to best use. The 4 programs
that did the best at this used:
C   + pthreads + INTEL sse2 intrinsics,
C++ + OpenMP   + INTEL sse2 intrinsics,
ATS + pthreads(?) + INTEL sse2 intrinsics,
and
Ada + Ada + Ada.

Jonathan