Feeds

Facing up to parallelism

Multicore means today's HPC is tomorrow's general purpose

High performance access to file storage

It is, perhaps, one of those forgotten facts that computing is still a relatively young technology, made all the more poignant by the realisation that many of the people driving the High Performance Computing (HPC) business, like Burton Smith, Microsoft's technical fellow in charge of advanced strategies and policies for the company, have not only been round the track several times, but are very much still at the bleeding edge of the technology.

Smith's track record includes many years as chief scientist at Cray, but his views now are hardly stuck in the past, for he believes that the parallel processing technologies that have been developed round HPC are where the mainstream of computing technology now has to head.

"We are now at the point where we are breaking the Von Neumann Assumption that there is only one program counter that allows the proper ordering and scheduling of variables," he said. "Parallel programming makes this hazardous, but we are also now at the point where serial programs are becoming slow programs."

Driving this is the arrival of multicore processor chips into the mainstream of computing. As the only way to get more performance of a single threaded processor is to increase its speed, and the only way to do that is via increased power consumption and all the costs associated with it, multicore chips offer a different, but inherently parallel alternative to boosting performance, and performance has always been the chief characteristic of HPC systems. So the lessons learned there can now start to be applied in general purpose computing.

"Computing must be reinvented, but many of those who invented computing are still alive. We did it once and we can do it again," he said.

"Reinvention" is, however, a potentially scary word, and Smith is aware of the dangers. This is particularly the case where there is such a long-standing installed base of applications, process, and operating methods as found in the mainstream business computing arena.

"Reinvention" could make all of that obsolete almost over night. It is not a route that he favours, however. "One option with the move to parallelisation is to simply wipe the slate clean and start again with something new," he said. "This is what I call the Apple approach, where a great new technology is introduced with not much thought given to the pain it might cause users of an earlier technology. But we have to take existing users with us."

Smith used his keynote presentation at the recent International Supercomputing Conference in Dresden, to take a look at what is happening to computing as a whole. The fundamental, he suggested, is that uniprocessor performance is levelling off and instruction levels, power consumption and cache limitations are all "walls" that are now being hit. And the fact that we now have multicore processors doesn't change this if the architecture hasn't changed, which then means that they become difficult to program.

The Instruction Level Wall is constructed from the limits of the uniprocessor instruction architecture, which are now being reached. There are issues that restrict the level of concurrency possible in a system, such as control dependent computation and data dependent memory addressing, and they collectively limit such architectures to a few instructions per clock cycle.

The Power Wall is now coming into play more significantly. As an example he noted that it is possible to scale hardware by Sigma, but that the power will scale by Sigma as well. Scaling the clock frequency by Sigma is worse, for it scales the dynamic power by Sigma cubed.

The Memory Wall needs not only bigger cache sizes, but also the ability to cut the cache miss-rate in half. In addition, the actual size of the growth in cache capacity will be driven by the type of data being fetched and stored. The more complex, the greater the cache needs to be. For example, if the data is intended for dense matrix-matrix multiply functions, then the cache needs to be four times bigger. If it is for a Fast Fourier transform it has to be the square of the original cache to half the miss-rate. So there are issues here in not only increasing cache size, but also increasing the bandwidth and reducing the latency of the channel serving the cache.

HPC technologies have, over the years, developed solutions to these problems. But they have also suffered from being caught in something of a self-serving spiral. As Smith put it: "HPC systems have been the ones that run HPC applications, while HPC applications are the ones that run on HPC systems."

So it might have remained if it had not been for the application of dual-core, and now multicore, processors across the board. The same fundamental techniques of parallel processing now start to apply equally to mainstream business applications as to the most complex weather forecasting system.

High performance access to file storage

More from The Register

next story
Windows 8.1, which you probably haven't upgraded to yet, ALREADY OBSOLETE
Pre-Update versions of new Windows version will no longer support patches
Android engineer: We DIDN'T copy Apple OR follow Samsung's orders
Veep testifies for Samsung during Apple patent trial
OpenSSL Heartbleed: Bloody nose for open-source bleeding hearts
Bloke behind the cockup says not enough people are helping crucial crypto project
Microsoft lobs pre-release Windows Phone 8.1 at devs who dare
App makers can load it before anyone else, but if they do they're stuck with it
Half of Twitter's 'active users' are SILENT STALKERS
Nearly 50% have NEVER tweeted a word
Windows XP still has 27 per cent market share on its deathbed
Windows 7 making some gains on XP Death Day
Internet-of-stuff startup dumps NoSQL for ... SQL?
NoSQL taste great at first but lacks proper nutrients, says startup cloud whiz
US taxman blows Win XP deadline, must now spend millions on custom support
Gov't IT likened to 'a Model T with a lot of things on top of it'
prev story

Whitepapers

Mainstay ROI - Does application security pay?
In this whitepaper learn how you and your enterprise might benefit from better software security.
Five 3D headsets to be won!
We were so impressed by the Durovis Dive headset we’ve asked the company to give some away to Reg readers.
3 Big data security analytics techniques
Applying these Big Data security analytics techniques can help you make your business safer by detecting attacks early, before significant damage is done.
The benefits of software based PBX
Why you should break free from your proprietary PBX and how to leverage your existing server hardware.
Mobile application security study
Download this report to see the alarming realities regarding the sheer number of applications vulnerable to attack, as well as the most common and easily addressable vulnerability errors.