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Re: differences between implementations of IEEE-754 basic operators
David Hough 754R work <754r@xxxxxxxxxxx> wrote:
getting reproducible results ...
is effectively incompatible with most forms of parallelism.
Finding ANY useful form of parallelism in most programs is pretty hard.
How many laptop users can keep even three threads active?
I said MOST forms of parallelism. I am including the sort that
is included in an out-of-order processor, SIMD units and so on.
But the most typical type that can be profitably exploited is doing
the same or similar things at the same time, e.g. computing two or
more elements of a matrix product at once. That is perfectly
reproducible, with any number of processors.
Not once you permit exception handling, it isn't. And IEEE 754
does just that.
What is NOT reproducible is reduction operations ....
There are actually lots of other usages, too, but they are more
complicated.
Regards,
Nick Maclaren,
University of Cambridge Computing Service,
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England.
Email: nmm1@xxxxxxxxx
Tel.: +44 1223 334761 Fax: +44 1223 334679