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Supercomputers: Obama orders world's fastest computer

bbc.co.uk

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Re: Supercomputers: Obama orders world's fastest computer

#111

Post by ddingus »

jkot wrote: post #57
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?

I use i7 2600k at 5.0 GHz for some time. Probably best option for ordinary human.

Interesting! I'm running this one: Intel® Core™ i7-4790K at 4.x Ghz (currently 4.2 for long term big problem stability)

What does your setup look like? Cooling, RAM, etc...?

And is it good for long term, like say crunch on it for a week type problems?

Re: Supercomputers: Obama orders world's fastest computer

#112

Post by dekhn »

apawloski wrote: post #107
dekhn wrote: post #105

Earlier quoted context omitted.

No, the people who run the clusters won't let you run any language just because it has an MPI binding. They invest a lot in ensuring peak performance, and right now, only C++ and FORTRAN can achieve that. Very few, if any, major supercomputer centers support Java codes.

Oh, you're talking about a policy limitation, not a technological one. (And if you're talking about the DOE or NSF/Teragrid/XSEDE clusters, then you're probably right. Haven't touched those in years -- and even when I did, I wasn't doing anything crazy.)

To be frank, if I was running a computer that was designed for peak performance, I probably wouldn't use Java. There are some very significant performance issues with garbage collection that prevent you from making peak use of them machine.

Supercomputers aren't built so that people can squander the resource (desktop PCs, closest clusters, and phones fulfill that role).

Re: Supercomputers: Obama orders world's fastest computer

#113

Post by dekhn »

jedbrown wrote: post #101
ajdecon wrote: post #98

Earlier quoted context omitted.

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 perfor…

HPCG basically measures STREAM and has many technical flaws making it scale-dependent and difficulty to adjudicate. As codeveloper of a different benchmark, I'll just cite this paper from a third party. https://hpgmg.org/static/MarjanovicGraciaGlass-PerformanceMo... The reality is that there are many dimensions to supercomputing performance and it's impossible for one number to capture the utility of the machine. Our…

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?

Re: Supercomputers: Obama orders world's fastest computer

#114

Post by khm »

sevensor wrote: post #75
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…

> 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…

Ah, a Cray. Buck up; there are better supercomputers.

Re: Supercomputers: Obama orders world's fastest computer

#115

Post by scottcha »

ypcx wrote: post #106
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…

Clearly designed to run AI for cyber-warfare / cyber-defense purposes? William Gibson's Black Ice coming to life?

More likely its for modeling nuclear weapons which I believe is the primary purpose of NSCI.

Re: Supercomputers: Obama orders world's fastest computer

#116

Post by jandrewrogers »

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…

It is important to not conflate "massively parallel" (HPC) and "massively distributed" (Internet-scale), they have different architectural requirements and solve different classes of problem. People with competency in either of these areas tend to overestimate their understanding of the other but they are not solving the same computer science problems even though they look similar on the surface.

Massively distributed systems do not get much benefit from low-latency interconnects. Massively parallel systems do, and in particular, it is a "throw hardware at the problem" kind of solution that helps cover for the fact that virtually no software designers can engineer efficient, non-trivial, massively parallel systems. MapReduce is a distributed model; outside of some trivial cases, it is a poor parallel model. And while the HPC community has a much better understanding of massive parallelism than the Internet-scale systems community, the HPC community largely doesn't grok massively distributed systems in the way that someone working on Google's infrastructure would.

I benefitted from having spent several years designing software for both HPC and Internet-scale systems. They are not fungible, and both communities grok things that the other is oblivious to. Even within the HPC community though, the number of people skilled at the design of massively parallel software systems is quite small, much smaller than people that know massively distributed systems.

You do not need two systems, you need one system and more people that have figured out how to design massively parallel software -- the real problem. It is difficult to overstate just how rare this skill is even within the HPC community.

Re: Supercomputers: Obama orders world's fastest computer

#117

Post by trsohmers »

scottcha wrote: post #115
ypcx wrote: post #106

Earlier quoted context omitted.

Clearly designed to run AI for cyber-warfare / cyber-defense purposes? William Gibson's Black Ice coming to life?

More likely its for modeling nuclear weapons which I believe is the primary purpose of NSCI.

NNSA*, which is an office within the Department of Energy.

Re: Supercomputers: Obama orders world's fastest computer

#118

Post by trsohmers »

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.

Re: Supercomputers: Obama orders world's fastest computer

#119

Post by jedbrown »

dekhn wrote: post #113
jedbrown wrote: post #101

Earlier quoted context omitted.

HPCG basically measures STREAM and has many technical flaws making it scale-dependent and difficulty to adjudicate. As codeveloper of a different benchmark, I'll just cite this paper from a third party. https://hpgmg.org/static/MarjanovicGraciaGlass-PerformanceMo... The reality is that there are many dimensions to supercomputing performance and it's impossible for one number to capture the utility of the machine. Our…

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 CG or related algorithms, the bottlenecks depend on the scale, and ability to expose locality, and operator/preconditioner representation. If there is no locality, then matrix-vector products require all-to-all communication which tend to dwarf the cost of the reductions in CG. Even with locality in the matrix-vector product, preconditioners often need to communicate globally in a scalable way similar to HPGMG. Operators need not be represented as a table of numbers or a sparse matrix format, but could use a tensor product, fast transform, or other information to compute the action using less storage. If they are represented explicitly (sparse or dense), then matrix-vector product performance (thus CG as a whole) is dominated by memory bandwidth for problem sizes that do not fit in cache. HPGMG tries to strike a balance between memory bandwidth demands and compute using a matrix-free representation. HPGMG also reports dynamic range expressed as Performance versus Time-to-solution as the problem size is varied, which allows applications to see performance barriers that might be relevant to them (e.g., see how Titan cannot do a solve in less than 200 ms while Edison can do 50 ms, and how that relates to climate simulation performance targets; see slide 7 of https://jedbrown.org/files/20150624-Versatility.pdf).

Re: Supercomputers: Obama orders world's fastest computer

#120

Post by dekhn »

jandrewrogers wrote: post #116
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…

It is important to not conflate "massively parallel" (HPC) and "massively distributed" (Internet-scale), they have different architectural requirements and solve different classes of problem. People with competency in either of these areas tend to overestimate their understanding of the other but they are not solving the same computer science problems even though they look similar on the surface. Massively distribute…

I don't really agree with your premise.
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