How We'll Program 1000 Cores - and Get Linus Ranting, Again

vikingpower writes For developers, 2015 got kick-started mentally by a Linus Torvald rant about parallel computing being a bunch of crock. Although Linus' rants are deservedly famous for the political incorrectness and (often) for their insight, it may be that Linus has overlooked Gustafson's Law. Back in 2012, the High Scalability blog already ran a post pointing towards new ways to think about parallel computing, especially the ideas of David Ungar, who thinks in the direction of lock-less computing of intermediary, possibly faulty results that are updated often. At the end of this year, we may be thinking differently about parallel server-side computing than we do today.

Comments

Pullin' a Gates?

[Tablizer]

"4 cores should be enough for any workstation"

Perhaps it's an over-simplification, but if it turns out wrong, people will be quoting that for many decades like they do Gates' memory quote.

Re:Pullin' a Gates?

[bruce_the_loon]

If you went and read Linus' rant, then you'll find you are actually reinforcing his argument. He says that except for a handful of edge use-cases, there will be no demand for massively parallel in end user usage and that we shouldn't waste time that could be better spent optimizing the low-core processes.

The CAD, video and HTPC use-cases are already solved by the GPU architecture and don't need to be re-solved by inefficient CPU algorithms.

Your Linux workstation would be a good example, but is a very low user count requirement and can be done at the compiler level and not the core OS level anyway.

Your Linux gaming machine shouldn't be doing more than 3/4 cores of CPU and handing the heavy grunt work off to the GPU anyway. No need for a 64 core CPU for that one.

Redesigning what we're already doing successfully with a low number of controller/data shifting CPU cores managing a large bank of dedicated rendering/physics GPU cores and task-specific ASICs for things like 10GB networking and 6GB IO interfaces is pretty pointless, which is what Linus is talking about, not that we only need 4 cores and nothing else.

Bad summary, shocking

[Urkki]

Linus doesn't so much say that parallelism is useless, he's saying that more cache and bigger, more efficient cores is much better. Therefore, increased number of cores at the cost of single core efficiency is just stupid for general purpose computing. Better just stick more cache to the die, instead of adding a core. Or that is how I read what he says.

I'd say, number of cores should scale with IO bandwidth. You need enough cores to make parallel compilation be CPU bound. Is 4 cores enough for that? Well, I don't know, but if the cores are efficient (highly parallel out-of-order execution) and have large caches, I'd wager IO lags far behind today. Is IO catching up? When will it catch up, if it is? No idea. Maybe someone here does?