(j3.2006) Integration of co-arrays with the intrinsic shift functions

[keith bierman]

On Jul 12, 2007, at 3:14 PM, Andy Vaught wrote:

>
>   I'm not saying that your proposal is without merit or shouldn't be
> adopted, but you're moving into an area in which calculations will be
> irreproducible from run to run.
>
>

What language in the current (or previous) standards can you point to  
that requires reproducible results?

This isn't a new problem, but it certainly does get more obvious as  
parallelism and heterogeneous computing becomes more common. But even  
a uniprocessor with a single floating point unit (e.g. the 8087) can  
exhibit it (admittedly that's pathologically rare; but I've seen that  
sort of thing most of my life ... attached array processors, parallel  
processors, different steppings of multiprocessors, etc.).

As best I can tell, no Standard from 66 onward ever *required*  
reproducible results. Clearly, on conventional uniprocessors failure  
to do so is unexpected and is a quality of implementation issue. But  
on more exotic machines ... it's never been carved in stone.