Re: Please listen to Ulrich here...
On 2013-08-12 16:24:57 +0200, Ulrich Kulisch wrote:
> Dear David,
>
> I thank you again for your very interesting mail. It shows indeed that the
> long accumulator method is most energy efficient. Compared with computing a
> dot product by the conventional method in floating-point arithmetic it
> avoids a large number of data movements in the computer. [...]
That's probably true for this comparision. However "energy efficient"
is misleading. You must consider:
1. Does the long accumulator need energy
* when it isn't used at all?
* when it isn't used by an operation, but needs to retain
its memory?
2. What would be the loss/gain of energy if the long accumulator
were replaced by some other feature (e.g. to reduce the needed
energy for accurate polynomial evaluation)?
3. How much % of energy would you gain in average applications?
I suppose that in most applications, the long accumulator would
be useless, so that the % would be too low to have an interest
for processor vendors.
--
Vincent Lefèvre <vincent@xxxxxxxxxx> - Web: <http://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)