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

Andy Vaught andyv
Thu Jul 12 18:26:04 EDT 2007

nOn Thu, 12 Jul 2007, keith bierman wrote:

> 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.

  I did misunderstand Craig's original post and agree with you that the
language does not require it.

  However, if a language makes it easy to write programs that have
semi-random output, such programs become extraordinarily hard to debug and
will hopefully lead to the decline in the use of such a language.


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