Re: Real Time IO routines

[andrew <andrew.carroll@okstate.edu>]

On Oct 26, 3:33 pm, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> On Fri, 26 Oct 2007 13:00:13 -0700, andrew wrote:
> > On Oct 26, 1:36 pm, Ludovic Brenta <ludo...@ludovic-brenta.org> wrote:
> >> andrew writes:
> >>> Time_Unit is defined as a constant := 10#1.0#E-9, is Time_Unit then
> >>> a "real literal"?  How can I convert a "real literal" to a scalar
> >>> type (maybe that's a contradiction?)?
>
> >> Real literals are of the type universal_real which (a) is scalar and
> >> (b) converts implicitly to any other floating-point type.  Does that
> >> answer your question?
>
> > To Ludovic:  Ahh, so if I had to define a universal_real I could
> > output it using something like integer'image(it)?
>
> > To AV:  I don't really know why it's necessary yet; sometimes my
> > subconcious mind works faster than my concious mind and I just have to
> > go with it.  I can say though that:
>
> >    --  Time and Time_Span are represented in 64-bit Duration value in
> >    --  in nanoseconds. For example, 1 second and 1 nanosecond is
> >    --  represented as the stored integer 1_000_000_001.
>
> You never know, that depends on the underlying hardware and OS. Even under
> the same hardware/OS there exist multiple time sources with their own
> precision and accuracy.
>
> > So if a duration is represented as the stored INTEGER ... then I could
> > maybe use integer'image(duration), maybe?
>
> > what does this mean:  type DURATION is delta implementation_defined
> > range implementation_defined;?
>
> It varies from platform to platform
>
> > Is delta?  what's delta?
>
> Precision of a fixed-point type. See ARM 3.5.9.
>
> with Ada.Real_Time;  use Ada.Real_Time;
> with Ada.Text_IO;    use Ada.Text_IO;
>
> procedure Test is
>    Start  : Time := Clock;
>    Period : Duration;
>    type Seconds is delta 0.000_001 range -1.0E10 .. 1.0E10;
>       -- Microsecond precision type
> begin
>    delay 0.5;
>    Period := To_Duration (Clock - Start);
>    Put_Line ("Duration delta on this computer = " & Float'Image
> (Duration'Delta));
>    Put_Line (Duration'Image (Period) & "s");
>    Put_Line (Integer'Image (Integer (Period * 1000.0)) & "ms");
>       -- Be careful here, as it might overflow first in the multiplication
>       -- and then in conversion to integer
>    Put_Line (Float'Image (Float (Period)) & "s");
>    Put_Line (Seconds'Image (Seconds (Period)) & "s");
> end Test;
>
> --
> Regards,
> Dmitry A. Kazakovhttp://www.dmitry-kazakov.de- Hide quoted text -
>
> - Show quoted text -

This is all great information; thank you all those that posted.

Something seems to be wrong though.  In my program I am basiclly
doing:

start := clock;
--I run my algorithm here
finish := clock;
ada.Text_IO.put_line("time = " & duration'image(to_duration(finish -
start)));

the output is always time = 0.000000000.  I know it had to take some
time because it takes about 10 seconds for the program to reach that
point in the code.  Overflow maybe?