Re: I vote NO on motion 21...
On 2010-12-04 19:15:08 -0800, Dan Zuras Intervals wrote:
> Folks,
>
> I vote NO on motion 21.
>
> My reason has nothing to do with the set of
> comparisons proposed. Any reasonable set is
> fine with me.
>
> The reason I vote NO is that the motion is
> written in a manner that suggests (or even
> implies) the existence of state attached to
> the act of making a comparison.
This is wrong: it doesn't suggest or imply anything like that (the
word "state" is used purely in an abstract specification; there are
no data formats with some state in them). Perhaps the wording isn't
perfect, but we are not voting on the wording.
> We wrote comparisons in a similar manner in
> 754-1985 & it led to implementers actually
> CREATING such state as 4 global variable
> bits usually in a PSW attached to the thread
> of execution in question.
>
> At the time & in the era of 4 MegaHz 8-bit
> microprocessors that implemented their
> floating-point in software more often than
> not, this was not considered bad.
So, what's wrong at that time?
> But in the years that have followed it has
> become clear that requiring state is a bad
> thing in the era of multi threaded multi
> GigaHz 32 or 64 bit microprocessors with
> multiple on chip floating-point units. It
> creates an interlock choke point similar to
> a branch that slows everything down & makes
> added headaches for the hardware designer.
They are not forced to use the same kind of implementation today.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)