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: 103376,349427c451f66022
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!weretis.net!feeder4.news.weretis.net!news.teledata-fn.de!newsfeed.arcor.de!newsspool1.arcor-online.net!news.arcor.de.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Strange behaviour of delay in Windows XP
Newsgroups: comp.lang.ada
User-Agent: 40tude_Dialog/2.0.15.1
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Reply-To: mailbox@dmitry-kazakov.de
Organization: cbb software GmbH
References: <i8lcl2$f0i$1@news.eternal-september.org>
Date: Fri, 8 Oct 2010 09:54:37 +0200
Message-ID: <16p5l53nudhpa.cxcrndddsok0.dlg@40tude.net>
NNTP-Posting-Date: 08 Oct 2010 09:54:38 CEST
NNTP-Posting-Host: 051afd2e.newsspool3.arcor-online.net
X-Trace: 
 DXC=J=ec3kle`UTaoembcbF;DQMcF=Q^Z^V3X4Fo<]lROoRQ8kF<OcfhCO[ZljGUOAYJ@W[6LHn;2LCV^7enW;^6ZC`T\`mfM[68DCSCmjJMDLoeVR
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news1.google.com comp.lang.ada:14432
Date: 2010-10-08T09:54:38+02:00
List-Id: <comp.lang.ada>

On Thu, 07 Oct 2010 23:04:33 +0200, michael bode wrote:

> I've seen a very strange behaviour of the delay statement with GNAT on a
> Windows XP machine. This is the code:
> 
> with  Ada.Text_Io; use Ada.Text_Io;
> with Ada.Calendar; use Ada.Calendar;
> 
> procedure Testprog is
>    T1, T2 : Time;
>    D : Duration;
> begin
>    D := 1.0;
>    T1 := Clock;
>    delay D;
>    T2 := Clock;
>    Put_Line ("Expected delay:" & Duration'Image(D));
>    Put_Line ("Actual delay:" & Duration'Image(T2-T1));
> end Testprog;
> 
> And this is what it prints when run on Linux:
> 
> Expected delay: 1.000000000
> Actual delay: 1.000321000
> 
> But I have a (or rather 2) Dell Vostro MT 220 PC where the actual delay
> is about 2.7s instead.

What happens with this:

with Ada.Text_IO;    use Ada.Text_IO;
with Ada.Calendar;   use Ada.Calendar;
with Win32.Mmsystem; use Win32.Mmsystem;
with Win32.WinBase;  use Win32.WinBase;

procedure Testprog is
   T1, T2 : Time;
   D : Duration;
   use type Win32.BOOL;
begin
   if TIMERR_NOERROR /= timeBeginPeriod (1) then
      raise Program_Error;
   end if;
   if 0 = SetThreadPriority (GetCurrentThread,
THREAD_PRIORITY_TIME_CRITICAL) then
      raise Program_Error;
   end if;
   delay 1.0; -- Let the dust settle down
   D := 1.0;
   T1 := Clock;
   delay D;
   T2 := Clock;
   Put_Line ("Expected delay:" & Duration'Image(D));
   Put_Line ("Actual delay:" & Duration'Image(T2-T1));
end Testprog;

timeBeginPeriod (1) changes the resolution of timer to 1ms. Some older
systems had 10ms by default.

SetThreadPriority changes the priority to R-T.

> Any ideas or should I call a feng shui master?

Turn down indexing service, anti-virus software and whatever mess is
running on the computer in background.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de