Implement the "unum" representation in D ?

Ola Fosheim Grøstad via Digitalmars-d digitalmars-d at puremagic.com
Wed Sep 16 01:53:22 PDT 2015


On Wednesday, 16 September 2015 at 08:17:59 UTC, Don wrote:
> I'm not convinced. I think they are downplaying the hardware 
> difficulties. Slide 34:

I don't think he is downplaying it. He has said that it will 
probably take at least 10 years before it is available in 
hardware. There is also a company called Rex Computing that are 
looking at unum:

http://www.theplatform.net/2015/07/22/supercomputer-chip-startup-scores-funding-darpa-contract/

He assumes that you use a scratchpad (a big register file), not 
caching, for intermediate calculations.

His basic reasoning is that brute force ubox methods makes for 
highly parallel calculations. It might be possible to design ALUs 
that can work with various unum bit widths efficiently (many 
small or a few large)... who knows. You'll have to try first.

Let's not forget that there is a _lot_ of legacy constraints and 
architectural assumptions in both x86 architecture.

> The energy comparisons are plain dishonest. The power required 
> for accessing from DRAM is the energy consumption of a *cache 
> miss* !! What's the energy consumption of a load from cache?

I think this argument is aiming at HPC where you can find funding 
for ASICs. They push a lot of data over the memory bus.



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