Supercomputers: Obama orders world's fastest computer • Hacker News Board

Re: Supercomputers: Obama orders world's fastest computer

#121

Post by dekhn » Thu, Jul 30, 2015, 6:53 PM UTC

jedbrown wrote: post #119

dekhn wrote: post #113

Earlier quoted context omitted.

How would you use a benchmark like this to predict the performance of a well-designed asynchronous parallel conjugate gradient solver, like most modern deep learning neural networks that run on Internet HPC machines?

CG isn't truly asynchronous due to its reductions. It can be pipelined in various ways (we have several implementations in PETSc), but performance requires a quality implementation of asynchronous reduction (e.g., MPI_Iallreduce) which the vendors have been slow about developing (I've been working with some on fixing this and Cray has made recent progress). With respect to deep learning and other applications using C…

You might want to read up on Sibyl.

Re: Supercomputers: Obama orders world's fastest computer

#122

Post by ghayes » Thu, Jul 30, 2015, 6:59 PM UTC

trsohmers wrote: post #118

phreeza wrote: post #27

A bit more informative is the actual fact sheet put out by the white house [1]. What they are really aiming for is exa scale computing, which they define as being capable of applying exaFlops to exabytes. From my limited knowledge, the latter will actually be the bigger deal. As pointed out elsewhere, an exaflop supercomputer will probably come around beforehand. [1] https://www.whitehouse.gov/sites/default/files/mic…

The real problem is getting 1 exaflop (or around it) within a reasonable power budget. The DOE's power budget for all of their supercomputing resources is 20 Megawatts, so at a full system level we would need to be at 50 GFLOPs per watt, while the best system right now is at 5.

> "I'd say they're targeting around 60 megawatts, I can't imagine they'll get below that," [Mark Parsons] commented. "That's at least £60m a year just on your electricity bill."

Re: Supercomputers: Obama orders world's fastest computer

#123

Post by jedbrown » Thu, Jul 30, 2015, 7:02 PM UTC

vmarsy wrote: post #73

davegardner wrote: post #14

10 years ago the fastest supercomputer was BlueGene/L which was rated at 136.8 TFlop/s. The current fastest supercomputer is rated at 33,862.7 TFlop/s, or 247 times faster. It seems to me that the aim of taking 10 years to build a supercomputer that is only 20 times faster than the current one might fall a little short if it's aiming to take the top spot.

This isn't only about the FLOPS, the big trend of these countries* ordering new supercomputers by 2020/2025 is very focused on power. Current supercomputers consume a lot. Also the FLOPS measurement is a bit broken: It focuses on dense linear algebra problem, for which GPU or other accelerators boost the results easily. If all you plan to do is running simulations that are easily parallelized on GPU it is fine, for o…

Power is over-emphasized in HPC circles. According to FOIA reports (and you can back out similar from public budget information), less than 10% of the budget is going to energy. It is frequently used as an excuse to build machines that are inappropriate for the science (not just "hard to program", but actually inappropriate in the sense that even with infinite programming effort, they deliver less scientific value than a more conventional architecture). There is some value in making scientists uncomfortable so that they think of creative algorithmic solutions that may pay off as the inevitabilities of semiconductor physics become more apparent, but seeing the number of applications that are within small constant factors of proven barriers and the willingness to compromise quality of solution and/or run scientifically irrelevant configurations to demonstrate "speedup", I think it has gone too far.

Re: Supercomputers: Obama orders world's fastest computer

#124

Post by nickpsecurity » Thu, Jul 30, 2015, 7:05 PM UTC

Step 1: Order exascale computer. Step 2: ??? Step 3: Profit.

U.S. and other countries have been in a race for exascale. The thing holding us back isn't funding or political will: exascale is so ridiculously hard that it requires fundamentally different architectures. The main issues are making our CPU's do more work, eliminating memory bottlenecks, and dramatically improving energy efficiency of both. It's just very tough, technical challenges that might also have to operate on process nodes that are themselves tough.

Rexx Computing is one attempt whose founder posts here a lot [except in one thread dedicated to it lol]. I'm curious if any other exascale researchers read HN and can post their concepts as it's probably interesting stuff. Here's some links for readers interested in this stuff.

LLNL gives data on exascale and its challenges https://asc.llnl.gov/content/assets/docs/exascale-white.pdf

Also describes problems but skip to Venray's TOMI approach http://www.edn.com/design/systems-design/4368705/The-future-...

Rexx Computing's approach http://www.theplatform.net/2015/03/12/the-little-chip-that-c...

Intel's relatively conventional approach http://www.exascale-computing.eu/wp-content/uploads/2012/02/...

Architecture from Univ of Texas and NVIDIA https://www.cs.utexas.edu/users/skeckler/pubs/SC_2014_Exasca...

Boise exploring non-Von-Neuman with ParalleX http://cswarm.nd.edu/news-events/assets/PSAAP_II_Kick-off_CS...

Same group enlightens on details that all fight with http://sites.ieee.org/boise-cs/files/2015/04/Thomas-Sterling...

Bonus: 1,000 core, cache-coherent, optical interconnect. Sort of thing might be useful in exascale. http://dspace.mit.edu/openaccess-disseminate/1721.1/67490

Have fun with these. Submit a link if I left out any chip architecture in exascale race that's pretty cool.

Re: Supercomputers: Obama orders world's fastest computer

#125

Post by nickpsecurity » Thu, Jul 30, 2015, 7:06 PM UTC

phreeza wrote: post #21

davegardner wrote: post #14

10 years ago the fastest supercomputer was BlueGene/L which was rated at 136.8 TFlop/s. The current fastest supercomputer is rated at 33,862.7 TFlop/s, or 247 times faster. It seems to me that the aim of taking 10 years to build a supercomputer that is only 20 times faster than the current one might fall a little short if it's aiming to take the top spot.

The extrapolation on the top500 supercomputer list [1] estimates the first EFlop computer in 2019. The math in the article is weird. They say 20x faster, but 20x33 PFlops is quite a bit less than 1EFlop. [1] http://www.top500.org/statistics/perfdevel/

See my comment above. Has all the numbers you might need.

Re: Supercomputers: Obama orders world's fastest computer

#126

Post by nickpsecurity » Thu, Jul 30, 2015, 7:07 PM UTC

angdis wrote: post #20

I suppose that "supercomputers" are all multi-processor these days, so the colossal FLOP numbers are counted as an aggregation over many processors and one has to coordinate these processors in any application that takes advantage of the FLOP specs. Now I am curious what is the fastest single processor?

See my comment above for exascale info. The single chip performance will vary wildly. The important measurement is how many operations of useful work per second per watt the system will do. That's the gist of it I've learned from HPC people.

Exascale is power-hungry so power must go way down and efficiency of calculation way up.

Re: Supercomputers: Obama orders world's fastest computer

#127

Post by srdev » Thu, Jul 30, 2015, 7:09 PM UTC

DanBC wrote: post #3

codewithcheese wrote: post #2

Can anyone provide back of the napkin calculations on this proposed supercomputers computing power vs Googles compute farm?

or the Bitcoin farmers?

Comparing Bitcoin miners to any supercomputer or server farm is meaningless at best and deceiving at worst. Current Bitcoin miners cannot do anything other than one specific calculation.

Re: Supercomputers: Obama orders world's fastest computer

#128

Post by jerven » Thu, Jul 30, 2015, 7:12 PM UTC

juliangregorian wrote: post #108

lorenzhs wrote: post #88

Earlier quoted context omitted.

The term "embarrassingly parallel" doesn't refer to algorithms , it refers to problems which can be computed in such a manner, stating that they're not very interesting for parallel algorithms research. But yeah, it's kind of a stupid term. Would you be okay with "pleasingly parallel"? ;)

Potato, potato. I don't make the rules. I just think "embarrassingly parallel" sounds like a college freshman trying way too hard to sound smart and cool.

It called "embarrassingly parallel" because it is embarrassing for the Cray and other supercomputer vendors sales people when their expensive hardware does not outperform a 5 year old solution that cost 1/2 their fancy gear ;)

Otherwise data parallel is an other phrase that is used for the same concept.

Re: Supercomputers: Obama orders world's fastest computer

#129

Post by rwallace » Thu, Jul 30, 2015, 7:41 PM UTC

dekhn wrote: post #90

rwallace wrote: post #87

Earlier quoted context omitted.

That's true for many purposes, but is it true for physical simulations? Don't they need communication on every time step?

I would say no. Here is my argument: when I worked for DOE, everybody told me I had to run my MD simulations on a super computer using all the processors, and I would judged on my parallel efficiency. This meant using a code that used MPI to communicate at every (or every N) timesteps. I asked, instead, "Why not just run N independent simulations, and pool the results?" In this case, you run an M-thread simulation on…

Interesting! Would it be accurate to say that as the amount of computing power and memory per CPU has increased over the years, so also has the percentage of scientific problems where a single simulation instance will fit on a single CPU? Certainly if you can do so, it's more efficient (in both machine and human resources) to partition by one job per CPU.

Re: Supercomputers: Obama orders world's fastest computer

#130

Post by trsohmers » Thu, Jul 30, 2015, 7:44 PM UTC

ghayes wrote: post #122

trsohmers wrote: post #118

Earlier quoted context omitted.

The real problem is getting 1 exaflop (or around it) within a reasonable power budget. The DOE's power budget for all of their supercomputing resources is 20 Megawatts, so at a full system level we would need to be at 50 GFLOPs per watt, while the best system right now is at 5.

> "I'd say they're targeting around 60 megawatts, I can't imagine they'll get below that," [Mark Parsons] commented. "That's at least £60m a year just on your electricity bill."

I wouldn't trust a Brit to report the figures for the US Department of Energy. The DOE's budget is 20 Megawatts [source: http://science.energy.gov/~/media/ascr/ascac/pdf/meetings/20...]