From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,b49d3a703a4b4db5
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news3.google.com!feeder.news-service.com!85.214.198.2.MISMATCH!eternal-september.org!.POSTED!not-for-mail
From: Colin Paul Gloster <Colin_Paul_Gloster@ACM.org>
Newsgroups: comp.lang.ada
Subject: Re: compiler settings in AdaGIDE
Date: Tue, 27 Jul 2010 16:11:12 +0100
Organization: A noiseless patient Spider
Message-ID: 
 <alpine.LRH.2.00.1007271606050.27547@64bit-RedHat-Enterprise-Linux6beta>
References: 
 <c072b766-9241-4580-9447-4adeb6ed0573@x21g2000yqa.googlegroups.com>
 <e715e179-6053-4190-94d4-6a348f9ea635@q22g2000yqm.googlegroups.com>
Reply-To: Colin Paul Gloster <Colin_Paul_Gloster@ACM.org>
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Injection-Date: Tue, 27 Jul 2010 15:11:24 +0000 (UTC)
Injection-Info: mx02.eternal-september.org;
 posting-host="kheEuXGHhE2Z5eF1gAST+A";
	logging-data="9717"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX1+FjRIJxTTPwAay1Hw7gWhvqQ3ab6AP/9gVZ7xmdpelkQ=="
User-Agent: Alpine 2.00 (LRH 1167 2008-08-23)
In-Reply-To: 
 <e715e179-6053-4190-94d4-6a348f9ea635@q22g2000yqm.googlegroups.com>
Cancel-Lock: sha1:2uG80KacehY99DeWEh/yBYRml00=
X-X-Sender: Colin_Paul@64bit-RedHat-Enterprise-Linux6beta
Xref: g2news1.google.com comp.lang.ada:12607
Date: 2010-07-27T16:11:12+01:00
List-Id: <comp.lang.ada>

On Sat, 24 Jul 2010, Jonathan sent:

|----------------------------------------------------------------------|
|"[..]                                                                 |
|                                                                      |
|   time ./bench                                                       |
|                                                                      |
|Let's look at the best results first, and compare the                 |
|'09 and '10 GNAT GPL compilers:                                       |
|                                                                      |
|   2010 GNAT GPL:                                                     |
|   gnatmake bench.adb -gnatnp -O2 -march=native -ffast-math -funroll- |
|loops                                                                 |
|   3.61 seconds                                                       |
|                                                                      |
|   2009 GNAT GPL:                                                     |
|   gnatmake bench.adb -gnatnp -O2 -march=native -ffast-math -funroll- |
|loops                                                                 |
|   4.57 seconds                                                       |
|                                                                      |
|This came as a nice surprise to me!                                   |
|We can learn some more about the compiler switches by                 |
|toggling them. I'll stick to the 2010 GNAT GPL from now on:           |
|                                                                      |
|   change -O2 to -O3:                                                 |
|   (gnatmake bench.adb -gnatnp -O3 -march=native -ffast-math -funroll-|
|loops)                                                                |
|   running time changes from 3.61 to 3.63 seconds                     |
|                                                                      |
|   remove -funroll-loops:                                             |
|   (gnatmake bench.adb -gnatnp -O2 -march=native -ffast-math)         |
|   running time changes from 3.61 to 3.66 seconds                     |
|                                                                      |
|   remove -ffast-math:                                                |
|   (gnatmake bench.adb -gnatnp -O2 -march=native)                     |
|   running time changes from 3.61 to 4.35 seconds                     |
|                                                                      |
|The -ffast-math had an amazing affect. I've never seen that           |
|before ... maybe an interaction with complex number arithmetic.       |
|                                                                      |
|[..]"                                                                 |
|----------------------------------------------------------------------|

The GNU Compiler Collection's  -ffast-math  switch used to provide a
significant increase in speed for various frontends excluding GNAT. In
my experience at least, this effect had no special relationship with
complex numbers.