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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Strange behaviour of delay in Windows
Date: Tue, 26 Oct 2010 03:08:03 +0200
Organization: Ada @ Home
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Date: 2010-10-26T03:08:03+02:00
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Le Thu, 07 Oct 2010 19:35:36 +0200, Michael Bode <m.g.bode@web.de> a =C3=
=A9crit:

Unless the compiler conforms to the Real-Time Annex D, this accuracy is =
 =

implementation defined, which you can understand as =E2=80=9Csee the com=
piler  =

manual instead of the reference=E2=80=9D or alternatively as =E2=80=9Cyo=
u cannot assert  =

anything=E2=80=9D. This all said in 9.6(20) of the Ada 2005 RM :

    The time base associated with relative delays is as defined in D.9,
    =E2=80=9CDelay Accuracy=E2=80=9D or is implementation defined.

I know Dmitry Kazavov may have something to say about tasking and timing=
  =

in the Windows operating system.

To push the test further, did you tried a =E2=80=9Cdelay until =E2=80=A6=
=E2=80=9D statement, just  =

to see ?

> I would expect the delay statement to delay execution for the given
> time. So with this 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 :=3D 1.0;
>    T1 :=3D Clock;
>    delay D;
>    T2 :=3D Clock;
>    Put_Line ("Expected delay:" & Duration'Image(D));
>    Put_Line ("Actual delay:" & Duration'Image(T2-T1));
> end Testprog;
>
> I'd expect to get this result:
>
> Expected delay: 1.000000000
> Actual delay: 1.000239000
>
> But on one Windows machine (a Vostro MT 220, Windows XP) I get an actu=
al
> delay of about 2.7s instead. I tried with GNAT GPL 2008 and 2009. Ther=
e
> was no noticeable CPU load during the test. To make things more
> interesting, a different machine (Vostro MT 230, same RAM, same CPU, s=
ame
> Windows XP version) works as expected. And to make things even more
> interesting, the Vostro MT 220 normaly lives in the lab. When I found
> this bug I carried it over to my office to check things. In the office=

> it worked ok. Back to the lab and I got the 2.7s, most of the time. A
> couple of times I got 1.0xxx seconds.
>
> Then I compiled the program statically linked on Debian, put a Ubuntu
> Live CD in the machine and tried my program. Result was dozens of time=
s
> as printed above: 1.000xxx seconds.
>
> Any ideas?


-- =

Si les chats miaulent et font autant de vocalises bizarres, c=E2=80=99es=
t pas pour  =

les chiens.