Earlier quoted context omitted.
Serious question: what's left to model? They're already big enough to kill everyone, and we have heaps of them.
Often they model how the warhead ages, rather than how it explodes.
Yes, this is my understanding.
Supercomputers: Obama orders world's fastest computer
161–170 of 179 posts
Re: Supercomputers: Obama orders world's fastest computer
#162Earlier quoted context omitted.
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.
Yes, for example when I did my PhD work ~2001 with a T3E I could run a simulation of a duplex DNA in a box of water by running it in parallel. This was true both for memory and CPU reasons. It limited to me studying a single sequence at a time, or 2-3 which was the practical limit on the number of concurrent jobs. This used the well-balanced design of the T3E, which had a great MPI system. Eventually it reached the p…
none of this is news - what you're describing is really just strong scaling. and sure, most systems already have subsets of nodes set aside for post-simulation cleanup.
Re: Supercomputers: Obama orders world's fastest computer
#163too bad for him that he didn't order it earlier, maybe he could have figured out a way to stay for more then 8 years as President...
Re: Supercomputers: Obama orders world's fastest computer
#164Step 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…
Step 1: Nuclear test ban treaty. Step 2: Avoid nuclear test disasters. Step 3: Maintain military status quo.
Notice step 3 implies international stability and hence profit. NNSA stresses computation so heavily because stockpile stewardship cannot be done by noncomputational means.
Re: Supercomputers: Obama orders world's fastest computer
#165Step 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…
Step 1: Nuclear test ban treaty. Step 2: Avoid nuclear test disasters. Step 3: Maintain military status quo. Notice step 3 implies international stability and hence profit. NNSA stresses computation so heavily because stockpile stewardship cannot be done by noncomputational means.
Interesting point. Exascale is a lot more than that though: many stakeholders. And, even if none, it's still going to get funded as another international pissing contest (see Top 500). ;)
Re: Supercomputers: Obama orders world's fastest computer
#166Earlier quoted context omitted.
Nvidia's Pascale GPU, due next year, is supposed to do 28 terraflops with 1300 watts which I make 21 GFLOPs per watt.
That's single precision, which the DOE doesn't care about. The latest NVIDIA GPU's do 8 to 16 times better at single precision (32 bit) floating point compared to double precision (64 bit). The best next generation DP GFLOPs/watt from one of the big players will most likely be the 2016 Xeon Phi, at ~10-12GFLOPs/watt... You are also forgetting that GPUs also have a ~100W+ CPU sitting next to it, which brings down tota…
Your chip looks cool. I guess it may be tricky to adapt software to run on the thing? Or else you could try to sell Obama 4 million of them for his new computer.
Re: Supercomputers: Obama orders world's fastest computer
#167Earlier quoted context omitted.
It was, in fact. How did you infer that?
/scratch on a Cray is (last I used one) is a Lustre filesystem. It is the only file storage available to the compute nodes, which have no local storage of their own. No spinning disk, no SSD. So if the code is written such that it makes frequent small writes (e.g. it's peppered with print statements), the lustre nodes get hammered by all the compute nodes and become the bottleneck and they will eventually fall over.
Interesting! This was exactly the case on the system I used. I didn't realize Cray was the only vendor who went the no-local-storage route.
Re: Supercomputers: Obama orders world's fastest computer
#168Earlier 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…
Is it possible to calculate the theoretical performance of a cluster under HPGMG and then do a practical run and come with an efficiency number like in HPL ?
One of the biggest reasons for use of HPL is that many sizing considerations can be based off of the theoretical calculations.
But anyway this is very interesting. I definitely need to check this out.
Re: Supercomputers: Obama orders world's fastest computer
#169Earlier quoted context omitted.
Yes, for example when I did my PhD work ~2001 with a T3E I could run a simulation of a duplex DNA in a box of water by running it in parallel. This was true both for memory and CPU reasons. It limited to me studying a single sequence at a time, or 2-3 which was the practical limit on the number of concurrent jobs. This used the well-balanced design of the T3E, which had a great MPI system. Eventually it reached the p…
none of this is news - what you're describing is really just strong scaling. and sure, most systems already have subsets of nodes set aside for post-simulation cleanup.
Here is the news: the Jupiter paper is now published.
http://conferences.sigcomm.org/sigcomm/2015/pdf/papers/p183....
I'm not just describing strong scaling. I'm describing a cost-effective way to achieve it; that's what really matters.
Why have subsets of nodes for post-simulation cleanup? Why not just run that cleanup on the same nodes you used for simulation? Or other general nodes? Otherwise, you've got two sets of nodes which are used at lower utilization than they would normally be.
Re: Supercomputers: Obama orders world's fastest computer
#170Earlier quoted context omitted.
Well my point exactly. That "ton of design and equipment" doesn't scale particularly well, as its cost grows highly super-linearly with the computing power. You need to reduce communication volume to be cost effective at exascale.
This isn't true. You can build awesome high bandwidth clusters for extremely cheap. It takes an understanding of ethernet silicon and TCP implementations, but it can be done. Amazon for example recognized that superlinear cost scaling was killing their profits, and invested in building newer systems with better designs that solve these problems. See also this paper http://research.google.com/pubs/pub36740.html The ma…
here we go, the Jupiter paper is now published:
http://conferences.sigcomm.org/sigcomm/2015/pdf/papers/p183....