Opportunity: Software Execution Time Determinism

[dgls via Digitalmars-d]

 From my understanding of real-time systems WCET typically depends 
not only on the architecture of the target platform, but also on 
the criticality of the system.

On Thursday, 14 April 2016 at 08:14:59 UTC, Johannes Pfau wrote:
> Such deterministic code is usually very restricted. This is 
> expected. See also: 
> https://en.wikipedia.org/wiki/Worst-case_execution_time

Perhaps the best example of a restricted subset of a language 
would be Ada's ravenscar profile, for High integrity real-time 
systems:

http://www.dit.upm.es//~str/proyectos/ork/documents/RP_spec.pdf


> As a compiler we can't give a useful estimate of WCET without 
> knowing the target architecture very well (calculating some 
> upper bound is not too difficult, but if you ignore pipelining 
> and caches the calculated WCET might be 4-5x higher than the 
> real WCET).

I am agreed on this, I fail to see how a complier could provide 
any useful estimate. Not only does this measurement depend on the 
target hardware, but on the criticality of the task - a 
calculated upper bound is used for tasks with hard-deadlines, but 
measurement is usually sufficient for tasks with soft deadlines.