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From: BrianG <briang000@gmail.com>
Newsgroups: comp.lang.ada
Subject: Ada.Execution_Time
Date: Sat, 11 Dec 2010 23:19:50 -0500
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Has anyone actually used Ada.Execution_Time?  How is it supposed to be used?

I tried to use it for two (what I thought would be) simple uses: 
display the execution time of one task and sum the of execution time of 
a group of related tasks.

In both cases, I don't see anything in that package (or in 
Ada.Real_Time, which appears to be needed to use it) that provides any 
straightforward way to use the value reported.

For display, you can't use CPU_Time directly, since it's private.  You 
can Split it, but you get a Time_Span, which is also private.  So the 
best you can do is Split it, and then convert the parts to a type that 
can be used (like duration).

For summing, there is "+", but only between CPU_Time and Time_Span, so 
you can't add two CPU_Times.  Perhaps you can use Split, sum the 
seconds, and then use "+" to add the fractions to the next Clock (before 
repeating Split/add/"+" with it, then you need to figure out what to do 
with the last fractional second), but that seems an odd intended use.

The best I could come up with was to create my own function, like this 
(using the same definition for T as in Clock), which can be used for both:

function Task_CPU_Time return Duration (T : ...) is
    Sec      : Ada.Execution_Time.Seconds_Count;
    Fraction : Ada.Real_Time.Time_Span;
begin
    Ada.Execution_Time.Split(Ada.Execution_Time.Clock(T), Sec, Fraction);
    return To_Duration(Ada.Real_Time.Seconds(Integer(Sec)))
         + To_Duration(Fraction);
end Task_CPU_Time;

Wouldn't it make sense to put something like this into that package? 
Then, at least, there'd be something that's directly available to use - 
and you wouldn't need another package.  (I'm not sure about the 
definitions of CPU_Time and Duration, and whether the conversions would 
be guaranteed to work.)

--BrianG