Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

More Chip Cores Can Mean Slower Supercomputing, Simulation Shows

16.01.2009
THE MULTICORE DILEMMA: more cores on a single chip don't necessarily mean faster clock speeds, a Sandia simulation has determined.

The worldwide attempt to increase the speed of supercomputers merely by increasing the number of processor cores on individual chips unexpectedly worsens performance for many complex applications, Sandia simulations have found.

A Sandia team simulated key algorithms for deriving knowledge from large data sets. The simulations show a significant increase in speed going from two to four multicores, but an insignificant increase from four to eight multicores. Exceeding eight multicores causes a decrease in speed. Sixteen multicores perform barely as well as two, and after that, a steep decline is registered as more cores are added.

The problem is the lack of memory bandwidth as well as contention between processors over the memory bus available to each processor. (The memory bus is the set of wires used to carry memory addresses and data to and from the system RAM.)

A supermarket analogy

To use a supermarket analogy, if two clerks at the same checkout counter are processing your food instead of one, the checkout process should go faster. Or, you could be served by four clerks.

Or eight clerks. Or sixteen. And so on.

The problem is, if each clerk doesn’t have access to the groceries, he or she doesn’t necessarily help the process. Worse, the clerks may get in each other’s way.

Similarly, it seems a no-brainer that if one core is fast, two would be faster, four still faster, and so on.

But the lack of immediate access to individualized memory caches — the “food” of each processor — slows the process down instead of speeding it up once the number of cores exceeds eight, according to a simulation of high-performance computers by Sandia’s Richard Murphy, Arun Rodrigues and former student Megan Vance.

“To some extent, it is pointing out the obvious — many of our applications have been memory-bandwidth-limited even on a single core,” says Rodrigues. “However, it is not an issue to which industry has a known solution, and the problem is often ignored.”

“The difficulty is contention among modules,” says James Peery, director of Sandia’s Computations, Computers, Information and Mathematics Center. “The cores are all asking for memory through the same pipe. It’s like having one, two, four, or eight people all talking to you at the same time, saying, ‘I want this information.’ Then they have to wait until the answer to their request comes back. This causes delays.”

“The original AMD processors in Red Storm were chosen because they had better memory performance than other processors, including other Opteron processors, “ says Ron Brightwell. “One of the main reasons that AMD processors are popular in high-performance computing is that they have an integrated memory controller that, until very recently, Intel processors didn’t have.”

Multicore technologies are considered a possible savior of Moore’s Law, the prediction that the number of transistors that can be placed inexpensively on an integrated circuit will double approximately every two years.

“Multicore gives chip manufacturers something to do with the extra transistors successfully predicted by Moore’s Law,” Rodrigues says. “The bottleneck now is getting the data off the chip to or from memory or the network.”

A more natural goal of researchers would be to increase the clock speed of single cores, since the vast majority of applications are designed for single-core performance on word processors, music, and video applications. But power consumption, increased heat, and basic laws of physics involving parasitic currents meant that designers were reaching their limit in improving chip speed for common silicon processes.

“The [chip design] community didn’t go with multicores because they were without flaw,” says Mike Heroux. “The community couldn’t see a better approach. It was desperate. Presently we are seeing memory system designs that provide a dramatic improvement over what was available 12 months ago, but the fundamental problem still exists.”

In the early days of supercomputing, Seymour Cray produced a superchip that processed information faster than any other chip. Then a movement — led in part by Sandia — proved that ordinary chips, programmed to work different parts of a problem at the same time, could solve complex problems faster than the most powerful superchip. Sandia’s Paragon supercomputer, in fact, was the world’s first parallel processing supercomputer.

Today, Sandia has a large investment in message-passing programs. Its Institute for Advanced Architectures, operated jointly with Oak Ridge National Laboratory (ORNL) and intended to prepare the way for exaflop computing, may help solve the multichip dilemma.

ORNL’s Jaguar supercomputer, currently the world’s fastest for scientific computing, is a Cray XT model based on technology developed by Sandia and Cray for Sandia’s Red Storm supercomputer. Red Storm’s original and unique design is the most copied of all supercomputer architectures.

The current work was funded by Sandia’s Laboratory-Directed Research and Development office.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.

Neal Singer | Newswise Science News
Further information:
http://www.sandia.gov

More articles from Information Technology:

nachricht Information integration and artificial intelligence for better diagnosis and therapy decisions
24.05.2017 | Fraunhofer MEVIS - Institut für Bildgestützte Medizin

nachricht World's thinnest hologram paves path to new 3-D world
18.05.2017 | RMIT University

All articles from Information Technology >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

New insights into the ancestors of all complex life

29.05.2017 | Earth Sciences

New photocatalyst speeds up the conversion of carbon dioxide into chemical resources

29.05.2017 | Life Sciences

NASA's SDO sees partial eclipse in space

29.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>