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

Re: Supercomputers: Obama orders world's fastest computer

#91

Post by sevensor » Thu, Jul 30, 2015, 4:16 PM UTC

lorenzhs wrote: post #86

sevensor wrote: post #75

Earlier quoted context omitted.

> especially when the community has little or no skill at building NG Internet HPC systems I would argue that the community of people who actually have the skills to take advantage of the interconnects in a classic HPC system is vanishingly small, and in consequence we've overbuilt them on an epic scale. Allow me to vent. I had the good fortune to have a login on a "petascale" HPC system, and access to an allocation…

I would argue that many of the failures you describe are due to a lack of libraries that can exploit these systems. You can't expect every biologist to be an expert in distributed computing. The HPC and algorithms communities failed to consider the users of these systems and happily tinkered in their academic niches. All the while, what was actually needed were easy to use libraries that allowed non-experts to benefi…

I completely agree. My point is, the workload was lots of jobs using 100 nodes or less and doing massive amounts of file IO, while the cluster was essentially designed to run very large physics simulations, one at a time. This was a cluster that didn't need to exist.

Re: Supercomputers: Obama orders world's fastest computer

#92

Post by dekhn » Thu, Jul 30, 2015, 4:17 PM UTC

lorenzhs wrote: post #78

dekhn wrote: post #45

It looks like they are explicitly saying they want to make a machine that works for both types of HPC -- classic low-latency high-bandwidth internode communication (physics simulations) and modern Internet-driver high-bandwidth storage/node communications. This is because the supercomputer community has long ignored the Internet-style of computation (MapReduce etc). But most of the new generation of scientists are ad…

One of the largest challenges in building an exascale cluster is communication. Computing power increases at a higher rate than memory throughput does, and memory throughput increases faster than communication infrastructure advances. Many argue that an exascale computer can only be cost efficient if the communication capabilities scale highly sublinearly with the computation done in the subsystems [1]. In particular…

You are incorrect saying MapReduce isn't locality aware. Hadoop supports machine, rack, row, and cluster locality scheduling.

Also, most modern Internet HPC systems dedicate a ton of design and equipment to having very high cross-sectional bandwidth, which enables the locality restrictions to be relaxed.

Re: Supercomputers: Obama orders world's fastest computer

#93

Post by amelius » Thu, Jul 30, 2015, 4:21 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…

> Also the FLOPS measurement is a bit broken

Does anybody have a better measurement?

Perhaps it could be the size of the matrix that can be inverted on it in an hour of time, with IEEE double precision floats, using some standard algorithm.

Re: Supercomputers: Obama orders world's fastest computer

#94

Post by dekhn » Thu, Jul 30, 2015, 4:30 PM UTC

apawloski wrote: post #80

jakub_h wrote: post #63

Earlier quoted context omitted.

And by "codes", you mean specific legacy software artifacts written in FORTRAN (note that I'm not even spelling it as Fortran)? Of course that's a problem.

Write in any language you want; that's irrelevant to the nature of the computations being done here. By codes they mean -- at the minimum -- pretty much anything that requires frequent communication between any or all nodes as a necessary part of computation. (For example, simulations across a large 3D space, where the changing states of particles on node A directly impacts the states of particles on adjacent nodes.)

You can't write your code in any language you want on a supercomputer.

Also, there is a wide range of literature about communication patterns for supercomputer apps; my argument is that often times, to solve the problem that matters, you may not actually need to run the simulation you think you do. It's more that people are just used to running that way.

For example, with MD, you can run 1 sim parallelized over 100 machines using tightly coupled communication (doesn't necessarily mean the forces and positions of every particle have to be shared between node decompositions) or run 100 sims over 100 machines, with no communication except for input and output files. The latter can often answer the same question far more cheaply.

Re: Supercomputers: Obama orders world's fastest computer

#95

Post by mathetic » Thu, Jul 30, 2015, 4:32 PM UTC

unfamiliar wrote: post #79

bjacobel wrote: post #15

> The supercomputer would be 20 times quicker than the current leading machine, which is in China. So given Moore's Law, by the time it's finished in 2025, it will be 50 times slower than 2025's fastest? Yes, yes, Moore's Law is slowing, transistors on a chip =/= flops, etc. Still seems like they'd want to aim higher than 20x in 10 years.

You're assuming the goal is to build the fastest supercomputer in the world. I think the goal is probably closer to "get the computing resources we need at the lowest cost".

Well, the title literally says "world's fastest computer."

Re: Supercomputers: Obama orders world's fastest computer

#96

Post by vmarsy » Thu, Jul 30, 2015, 4:36 PM UTC

amelius wrote: post #93

vmarsy wrote: post #73

Earlier quoted context omitted.

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…

> Also the FLOPS measurement is a bit broken Does anybody have a better measurement? Perhaps it could be the size of the matrix that can be inverted on it in an hour of time, with IEEE double precision floats, using some standard algorithm.

It depends, I meant broken if you plan to compute other types of problems. For instance some big graph problem instead of involving linear algebra. Then you would favor the benchmarks from http://www.graph500.org/.

But what if you want to optimize for programs that are communication intensive, or memory intensive?

Should the FLOPS of a very specific linear algebra suite be used as the metric of best computers?

Re: Supercomputers: Obama orders world's fastest computer

#97

Post by melling » Thu, Jul 30, 2015, 4:40 PM UTC

danharaj wrote: post #53

melling wrote: post #49

Earlier quoted context omitted.

No, militaries has been funding R&D long before the nuclear age. http://airandspace.si.edu/exhibitions/wright-brothers/online... Rather than tell us how much you hate the military and capitalism maybe you can figure out a better way? I'd love to see more non-military funding. Perhaps medical research could be used to increase public interest in funding supercomputer research?

> Rather than tell us how much you hate the military and capitalism maybe you can figure out a better way. Well, knowing a few scientists, I can say that I know well the creative and inquiring spirits that advance us. The world is structured so that the people who do the actual development and discovery have to sell their talents to the logic of property and capital, either directly, or to the government that enforce…

There may be a better solution. Just because no one has found it doesn't mean we can't do better. However, I'm not one for cursing the darkness. Light a small candle and lead the way.

Re: Supercomputers: Obama orders world's fastest computer

#98

Post by ajdecon » Thu, Jul 30, 2015, 4:47 PM UTC

amelius wrote: post #93

vmarsy wrote: post #73

Earlier quoted context omitted.

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…

> Also the FLOPS measurement is a bit broken Does anybody have a better measurement? Perhaps it could be the size of the matrix that can be inverted on it in an hour of time, with IEEE double precision floats, using some standard algorithm.

The "High Performance Conjugate Gradients" benchmark was proposed a couple years ago as an alternative metric for ranking supercomputers. Its proponents claim its behavior is more similar to real applications (irregular access patterns, lower ratio of computation to memory access, etc), compared to linear algebra problems like the "High Performance Linpack" benchmark currently used by the Top500.

The different performance numbers for top systems on HPCG vs HPL are pretty striking: http://www.hpcg-benchmark.org/custom/index.html?lid=155&slid...

Original proposal to use HPCG as an alternative to HPL for supercomputer rankings: http://www.sandia.gov/~maherou/docs/HPCG-Benchmark.pdf

Re: Supercomputers: Obama orders world's fastest computer

#99

Post by varelse » Thu, Jul 30, 2015, 4:55 PM UTC

I'd really love to see speed measured by performance by a single collective computation of an O(n) or O(n log n) algorithm. This would emphasize the importance of balancing communication performance with computation. Not holding my breath, the LINPACK is strong with these people...

Re: Supercomputers: Obama orders world's fastest computer

#100

Post by twoodfin » Thu, Jul 30, 2015, 4:59 PM UTC

graphene wrote: post #13

88e282102ae2e5b wrote: post #4

It kills me every time I read about how the world's nth-fastest computer is just used to simulate nuclear explosions, so it was a delight to see that they're planning on using this one for some good.

I don't know if this is what you're referring to, but a common application for government-owned supercomputers is simulating the degredation of nuclear warheads. The degradation of the fissile material as well as its surroundings is highly critical to a nation's security, and also very hard to model well. Of course in an ideal world those cycles would be used to help cure cancer, but given that these warheads exist,…

The old way to do that was to blow one of them up every so often. The Nuclear Test Ban Treaty put a stop to that.