By: sylt (no.delete@this.thanks.com), April 21, 2015 9:49 am
Room: Moderated Discussions
Ivan Godard (ivan.delete@this.millcomputing.com) on April 20, 2015 5:27 pm wrote:
> Ronald Maas (rmaas.delete@this.wiwo.nl) on April 19, 2015 9:53 am wrote:
>
> >
> > I agree with Ivan Godard observation that even the most advanced traditional processor core spent
> > a fraction of the transistors and energy on actual useful work, calculations, data moves, etc.
> >
> > But I think with a different approach he would have a far better chance of success:
> >
> > 1) As you mentioned in your post, there is no compiler for Mill. A while ago I asked him about it in this
> > forum, and he answered his team lacked bandwidth to spend
> > much effort building a compiler (or adapting GCC/LLVM).
> > If he would build a software model of the Mill and at the
> > same time build a compiler and profiling tools needed,
> > he would be able to test effectively which ideas work and which won't. There is literally tons of existing
> > open source code available that can be used as input to improve the design where needed.
>
> You seem to have mistaken limited resources for lack of interest :-) We are putting
> all we can into the tool chain. The software model of the Mill has been running in sim
> for six years now, although the Mill of six years ago is not the Mill of today.
>
> However, I differ with your belief that profiling tools and large test runs are essential to architecture design.
> Yes, they are important for tuning - say any gain less than a factor of two. However, gains larger than that
> are visible by inspection, and insight. Of course, we have no idea whether the gain of a given feature will be
> 3.17X or 3.82X - but we can see that it will be somewhere between 3X and 4X. It's the same slide-rule, back-of-the-envelope,
> order of magnitude guesstimation that they don't teach engineering students today :-)
>
In my experience this is only true for trivial things in architectures. For all complicated issues where there is any significant tradeoff to do, going with gut feeling often leads you down the wrong path for unexpected reasons. Most of the interesting things in the Mill architecture seems far from trivial...
> Ronald Maas (rmaas.delete@this.wiwo.nl) on April 19, 2015 9:53 am wrote:
>
> >
> > I agree with Ivan Godard observation that even the most advanced traditional processor core spent
> > a fraction of the transistors and energy on actual useful work, calculations, data moves, etc.
> >
> > But I think with a different approach he would have a far better chance of success:
> >
> > 1) As you mentioned in your post, there is no compiler for Mill. A while ago I asked him about it in this
> > forum, and he answered his team lacked bandwidth to spend
> > much effort building a compiler (or adapting GCC/LLVM).
> > If he would build a software model of the Mill and at the
> > same time build a compiler and profiling tools needed,
> > he would be able to test effectively which ideas work and which won't. There is literally tons of existing
> > open source code available that can be used as input to improve the design where needed.
>
> You seem to have mistaken limited resources for lack of interest :-) We are putting
> all we can into the tool chain. The software model of the Mill has been running in sim
> for six years now, although the Mill of six years ago is not the Mill of today.
>
> However, I differ with your belief that profiling tools and large test runs are essential to architecture design.
> Yes, they are important for tuning - say any gain less than a factor of two. However, gains larger than that
> are visible by inspection, and insight. Of course, we have no idea whether the gain of a given feature will be
> 3.17X or 3.82X - but we can see that it will be somewhere between 3X and 4X. It's the same slide-rule, back-of-the-envelope,
> order of magnitude guesstimation that they don't teach engineering students today :-)
>
In my experience this is only true for trivial things in architectures. For all complicated issues where there is any significant tradeoff to do, going with gut feeling often leads you down the wrong path for unexpected reasons. Most of the interesting things in the Mill architecture seems far from trivial...
