(j3.2006) F03/0084, was Re: Interp letter ballot #25
Bill Long
longb
Fri May 11 23:09:46 EDT 2012
On 5/11/12 5:56 PM, Dan Nagle wrote:
> Hello,
>
> On May 11, 2012, at 14:48 , Bill Long wrote:
>>
>> When you get to GPU-land, you end up returning .false. for many of the "ieee_support..." inquiries in Clause 14. Particularly, IEEE_SUPPORT_HALTING which is the one most people are interested in. (Among the small fraction of users who use any feature in Clause 14.)
>
>
> Most applications I've seen are coded for a combination of host
> and device. Exactly what IEEE modes mean in a heterogeneous environment
Right. And it is not always obvious whether a particular operation is
happening on one or the other.
> is unclear to me. I suspect that a great deal of work is required
> to make the contrary plainly appear. Indeed, in an environment
> supporting asynchronous execution, the precise meaning of an exception
An exception occurs at a particular instruction in the code, not at a
particular time. So asynchronous, by itself, is not a killer. (People
have been using exceptions in MPI codes for years.) However, with SIMD
instructions and multiple threads, things get even less precise.
Assuming exceptions are registered at all.
> is likewise unclear (at least to me). Perhaps the issue can be resolved,
> but portably?
The easy solution is to just give up and say the processor does not
support the feature. Fortunately, the standard effectively allows that
option.
Cheers,
Bill
>
--
Bill Long longb at cray.com
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