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From: Adam Jensen <hanzer@riseup.net>
Newsgroups: comp.lang.ada
Subject: Re: What is the current language profile for concurrent,
 multi-core, safety-critical, hard real-time systems?
Date: Tue, 1 Aug 2017 01:45:22 -0000 (UTC)
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Date: 2017-08-01T01:45:22+00:00
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On Mon, 31 Jul 2017 20:54:08 -0400, Dennis Lee Bieber wrote:

> On Tue, 1 Aug 2017 00:25:18 -0000 (UTC), Adam Jensen <hanzer@riseup.net>
> declaimed the following:
> 
> 
>>What is the current Ada language profile for concurrent, multi-core,
>>safety-critical, hard real-time systems?
> 
> 	As soon as you say "multi-core" you enter the realm of 
experimental
> science. For example -- in the four years I spent at GE Aviation,
> multi-core processors used in flight management software would be run
> with all but one core shutdown.
> 
> 	Reason: there has not been enough experience/study of how multiple
> cores/cache/etc. affect hard real-time latency (how can you evaluate
> WCET for a process on core-A when you don't have control of what happens
> on core-B, which could cause cache line flushing, etc. affecting the
> timing of core-A)
> 
> 	What multi-core processors I saw being used in development were 
for
> non-safety critical functions -- data logging type operations, wherein
> loss of the logging processor wouldn't affect the flight management
> system; only reducing the post-flight analysis capabilities should there
> be anomalous flight operations.

That's interesting, thanks. I've been looking at the ARM Cortex-R8[1] 
which seems like it might address some of these issues in its hardware 
architecture.

[1]: https://developer.arm.com/products/processors/cortex-r/cortex-r8

I suppose that mapping an Ada run-time system onto that specific hardware 
might require a significant investment.

But more simply, this web page <http://www.ada2012.org/> says: "Ravenscar 
for multiprocessor systems adapts a safe and widely used tasking profile 
to modern architectures". Doesn't that seem to suggest that there exists 
an Ada-2012 Ravenscar profile for multi-core systems? Is that mostly hype 
or hokum?