From: singo on
Dear Ada community,

I have recently become very interested of Ada 2005, and it's real-time
annex. However, as a new user of Ada I face some problems with the
software.

I cannot get the package Ada.Execution_Time to work with gnat,
although the gnat documentation says that the real-time annex is fully
supported... I use the gnat version 4.4 on a Ubuntu 9.10 distribution.

The typical error message I get is

gcc -c executiontime.adb
Execution_Time is not supported in this configuration
compilation abandoned

How can I configure gnat to support the Ada.Execution_Time package?

Hopefully somebody can help me!

Thanks in advance!

Ingo

Below follows an example program that generates the error messge.

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Real_Time; use Ada.Real_Time;
with Ada.Execution_Time;

procedure ExecutionTime is
task T;

task body T is
Start : CPU_Time;
Interval : Time_Span := Milliseconds(100);
begin
Start := Ada.Execution_Time.Clock;
loop
Put_Line(Duration'Image(Ada.Execution_Time.Clock - Start));
delay To_Duration(Interval);
end loop;
end T;
begin
null;
end ExecutionTime;

From: Dmitry A. Kazakov on
On Fri, 4 Dec 2009 03:09:35 -0800 (PST), singo wrote:

> I have recently become very interested of Ada 2005, and it's real-time
> annex. However, as a new user of Ada I face some problems with the
> software.
>
> I cannot get the package Ada.Execution_Time to work with gnat,
> although the gnat documentation says that the real-time annex is fully
> supported... I use the gnat version 4.4 on a Ubuntu 9.10 distribution.
>
> The typical error message I get is
>
> gcc -c executiontime.adb
> Execution_Time is not supported in this configuration
> compilation abandoned
>
> How can I configure gnat to support the Ada.Execution_Time package?
>
> Hopefully somebody can help me!
>
> Thanks in advance!
>
> Ingo
>
> Below follows an example program that generates the error messge.
>
> with Ada.Text_IO; use Ada.Text_IO;
> with Ada.Real_Time; use Ada.Real_Time;
> with Ada.Execution_Time;
>
> procedure ExecutionTime is
> task T;
>
> task body T is
> Start : CPU_Time;
> Interval : Time_Span := Milliseconds(100);
> begin
> Start := Ada.Execution_Time.Clock;
> loop
> Put_Line(Duration'Image(Ada.Execution_Time.Clock - Start));
> delay To_Duration(Interval);
> end loop;
> end T;
> begin
> null;
> end ExecutionTime;

I cannot tell anything about Ubuntu, but the program you provided contains
language errors.

It also has the problem that "delay" is non busy in Ada, i.e. the program
will count 0 CPU time for a very long time, at least under Windows, where
the system services, which I presume, Ada.Execution_Time relies on, are
broken.

Anyway, here is the code which works to me:

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Real_Time; use Ada.Real_Time;
with Ada.Execution_Time; use Ada.Execution_Time;

procedure ExecutionTime is
task T;
task body T is
Start : CPU_Time := Clock;
begin
loop
Put_Line (Duration'Image (To_Duration (Clock - Start)));
for I in 1..40 loop
Put ("."); -- This does something!
end loop;
end loop;
end T;
begin
null;
end ExecutionTime;

Under Windows this shows rather poor performance, which again is not
surprising, because as I said there is no way to implement
Ada.Execution_Time under Windows.

Maybe Linux counts CPU time better, I never investigated this issue.

--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
From: Georg Bauhaus on
singo schrieb:

> I cannot get the package Ada.Execution_Time to work with gnat,
> although the gnat documentation says that the real-time annex is fully
> supported... I use the gnat version 4.4 on a Ubuntu 9.10 distribution.

The reason are explained in the GNAT source files. The ones I have show
a note, after the � box:
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- A D A . E X E C U T I O N _ T I M E --
-- --
-- S p e c --
-- --
-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. In accordance with the copyright of that document, you can freely --
-- copy and modify this specification, provided that if you redistribute a --
-- modified version, any changes that you have made are clearly indicated. --
-- --
------------------------------------------------------------------------------

-- This unit is not implemented in typical GNAT implementations that lie on
-- top of operating systems, because it is infeasible to implement in such
-- environments.

-- If a target environment provides appropriate support for this package
-- then the Unimplemented_Unit pragma should be removed from this spec and
-- an appropriate body provided.

with Ada.Task_Identification;
with Ada.Real_Time;

package Ada.Execution_Time is
pragma Preelaborate;

pragma Unimplemented_Unit;


From: John B. Matthews on
In article
<5e5d6fb5-e719-4195-925c-d1286699393d(a)f16g2000yqm.googlegroups.com>,
singo <sander.ingo(a)gmail.com> wrote:

> I have recently become very interested of Ada 2005, and it's
> real-time annex. However, as a new user of Ada I face some problems
> with the software.
>
> I cannot get the package Ada.Execution_Time to work with gnat,
> although the gnat documentation says that the real-time annex is
> fully supported... I use the gnat version 4.4 on a Ubuntu 9.10
> distribution.
>
> The typical error message I get is
>
> gcc -c executiontime.adb
> Execution_Time is not supported in this configuration
> compilation abandoned

Georg Bauhaus has helpfully referred you to comments in
Ada.Execution_Time.

> How can I configure gnat to support the Ada.Execution_Time package?

I defer to Dmitry A. Kazakov about Windows, but this variation produces
similar results on MacOS 10.5 & Ubuntu 9.10 using GNAT 4.3.4:

<code>
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Real_Time; use Ada.Real_Time;

procedure ExecutionTime is
task T;

task body T is
Start : Time := Clock;
Interval : Time_Span := Milliseconds(100);
begin
loop
Put_Line(Duration'Image(To_Duration(Clock - Start)));
delay To_Duration(Interval);
end loop;
end T;
begin
null;
end ExecutionTime;
</code>

<console>
$ ./executiontime
0.000008000
0.100168000
0.200289000
0.300409000
0.400527000
0.500575000
....
</console>

--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>
From: Dmitry A. Kazakov on
On Fri, 04 Dec 2009 13:28:24 -0500, John B. Matthews wrote:

> In article
> <5e5d6fb5-e719-4195-925c-d1286699393d(a)f16g2000yqm.googlegroups.com>,
> singo <sander.ingo(a)gmail.com> wrote:
>
>> I have recently become very interested of Ada 2005, and it's
>> real-time annex. However, as a new user of Ada I face some problems
>> with the software.
>>
>> I cannot get the package Ada.Execution_Time to work with gnat,
>> although the gnat documentation says that the real-time annex is
>> fully supported... I use the gnat version 4.4 on a Ubuntu 9.10
>> distribution.
>>
>> The typical error message I get is
>>
>> gcc -c executiontime.adb
>> Execution_Time is not supported in this configuration
>> compilation abandoned
>
> Georg Bauhaus has helpfully referred you to comments in
> Ada.Execution_Time.
>
>> How can I configure gnat to support the Ada.Execution_Time package?
>
> I defer to Dmitry A. Kazakov about Windows, but this variation produces
> similar results on MacOS 10.5 & Ubuntu 9.10 using GNAT 4.3.4:
>
> <code>
> with Ada.Text_IO; use Ada.Text_IO;
> with Ada.Real_Time; use Ada.Real_Time;
>
> procedure ExecutionTime is
> task T;
>
> task body T is
> Start : Time := Clock;
> Interval : Time_Span := Milliseconds(100);
> begin
> loop
> Put_Line(Duration'Image(To_Duration(Clock - Start)));
> delay To_Duration(Interval);
> end loop;
> end T;
> begin
> null;
> end ExecutionTime;
> </code>
>
> <console>
> $ ./executiontime
> 0.000008000
> 0.100168000
> 0.200289000
> 0.300409000
> 0.400527000
> 0.500575000
> ...
> </console>

Your code counts the wall clock time. On the contrary Ada.Execution_Time
should do the task time, i.e. the time the task actually owned the
processor or, maybe, the time the system did something on the task's
behalf.

This package heavily depends on the OS services at least when the tasks are
mapped onto the OS scheduling items (like threads).

As far as I know it is impossible to implement it reasonably under Windows,
because the corresponding service (used by the Task Manager too) counts
time quants instead of the time. This causes a massive systematic error if
tasks are switched before they consume their quants. I.e. *always* when you
do I/O or communicate to other tasks. The bottom line, under Windows
Ada.Execution_Time can be used only for tasks that do lengthy computations
interrupted by only by the scheduler, so that all counted quants were
consumed and no time were spent in uncounted quants.

I don't know, if or how, this works under Linux or Max OS.

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