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From: Keean Schupke <keean.schupke@googlemail.com>
Newsgroups: comp.lang.ada
Subject: GNAT (GCC) Profile Guided Compilation
Date: Fri, 29 Jun 2012 02:17:19 -0700 (PDT)
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Date: 2012-06-29T02:17:19-07:00
List-Id: <comp.lang.ada>

I am developing a Monte-Carlo simulation engine, and I have implementations=
 in C++ and Ada. All performance figures come from the same reference hardw=
are. Both are built using GCC, and similar optimisation is applied to each =
(same optimisation level, cpu arch, inlining etc).

My C++ implementation achieves 40,000 simulations per second.

My Ada port initially achieves 32,000 iterations per second.

I refactored the Ada port to use System.Address to access the main data str=
ucture (as in the 'C++' version benchmarking showed a clear performance ben=
efit to *ptr_x compared to array[x])

The Ada port using System.Address achieves 40,000 simulations per second - =
so this is looking good.

However, when I use profile guided compilation, the C++ code performance le=
aps to 56,000 simulations per second, whereas the Ada only achieves 44,000 =
simulations per second.

Anyone have any ideas why profile guided compilation performs so poorly wit=
h Ada compared to C++? The initial with normal compilation seemed very prom=
ising.


Cheers,
Keean.