HPC 2017-18 | High-performance computing


work towards, the DOE’s current exascale goal is a good guide: an application that can run 50 times better than on today’s 20 Pflop systems, running under load at between 20 to 30 megawatts of power and with less than one fault per week. According to Robert Henschel, the SPEC


ACCEL single node benchmark is applicable to the future exascale system, but it would only evaluate a small section of a system – so a very comprehensive analysis, but not at scale. Posits could reset the approach of the community; first, it has to overcome natural scepticism and the current manufactured computer processors. Simon said that in his opinion the main


obstacle is that the global hardware computing industry is now a $350 billion enterprise. It will be very hard to move that market


Benchmarks should always be goal-based, but usually they are activity-based


towards innovative concepts like posit-based architectures, even if they are probably better. Marquardt also said, ‘Te concept of posits


is interesting but – at least at this point in time – is not expected to be of relevance for the next generation of supercomputers.’ Perhaps a breakthrough innovation will


variety of different frontier applications have become more important parameters than the obvious efficiency metrics, such as the number of cores, or the peak performance on some standard test suite.’ Leading thinkers in the US tend to agree on


this approach. ‘What is most important is that they all


have to measure progress on a metric that makes sense for the application. So there is no push to get some artificial results that may not make sense scientifically. Instead the application developers need to demonstrate a factor of a hundred improvement over 2017’s state-of-the-art in their chosen metric,’ said Simon. But is there an approach or benchmark


that will be able to meet the demands of future applications and their users, or will something new be needed for the ‘exa-age’ of supercomputing? ‘Tere is no overall best benchmark. Tese


benchmarks are not suited to actually make a purchase decision for a machine. You will need to first define what you want to accomplish


with a supercomputer,’ said Simon. Tese questions could be whether the


benchmark is for a single application or for a very diverse workload; or, is it for a small number of users or for many users – these are critical factors for managers of supercomputing systems. In many cases, one benchmark will be suitable for one problem, but not another. ‘For an actual procurement, the Sustained


Petascale Performance (SPP) is much more useful, but it needs to be tailored to the individual requirements,’ said Simon. Te Sustained Petascale Performance


metric tool is used on the Blue Waters system at the University of Illinois at Urbana- Champaign, US. It helps its users get a more detailed understanding of each application’s performance, workload and the overall continual performance of the entire system.


To posit-operation-per-second processors and beyond In an email interview, Dongarra emphasised that to get an idea of the best benchmark to


not come from one of the larger players, such as big chip manufacturers Intel or Nvidia, but a smaller start-up on the bleeding edge of technology. Start-up semiconductor company REX


Computing, based in the US, is developing a novel low-power processor chip called ‘Neo’. Tis 28 nanometre-sized technology is touted by its creators to have up to 25 times energy efficiency improvement for supercomputers and digital signal processing over conventional CMOS chips. REX Computing’s initial test chip was


produced last year and uses a custom-designed IEEE compliant floating point unit that is being sampled by early customers. Te team at REX are also experimenting


with posits and see great potential in them. A processor variant using posits is in production under contract with A*STAR. ‘We are a very small team, but are punching


outside our weight class,’ said Tomas Sohmers, CEO of REX Computing. ‘For a start-up like REX, we want to cater to early adopters and customers that have the absolute highest requirements for their systems, which


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