OpenACC Adds Support for OpenPOWER; Touts Growing Traction

By John Russell

June 13, 2016

In a show of strength leading up to ISC the OpenACC standards group today announced its first OpenPOWER implementation, the addition of three new members – University of Illinois, Brookhaven National Laboratory, and Stony Brook University – and details of its expanding 2016 training schedule. Michael Wolfe, technical director of OpenACC, also talked with HPCwire about thorny compiler challenges still remaining as the number of processor (all types) cores grows and memory management issues become more complex.

Currently in private beta testing and planned for public beta in August, the PGI OpenACC compiler supporting OpenPOWER has made steady progress according to Wolfe, who is also a compiler engineer with PGI (NVIDIA). “It includes the same command line. You can take an application, you copy all the sources, all the make files over, just type make, and it builds on the new system,” said Wolfe.

OpenACC (Open Accelerators) is the directives-based programming standard for parallel computing developed by Cray, Nvidia and PGI. The standard is designed to simplify parallel programming of heterogeneous CPU/GPU systems. As in OpenMP, the programmer can annotate C, C++ and Fortran source code to identify the areas that should be accelerated using compiler directives and additional functions. Like OpenMP 4.0 and newer, code can be started on both the CPU and GPU.[i]

The forthcoming version of PGI OpenACC compiler with OpenPOWER will feature:

  • Feature parity with PGI Compilers on Linux/x86+Tesla
  • CUDA Fortran, OpenACC, OpenMP, CUDA C/C++ host compiler
  • Integrated with IBM’s optimized LLVM OpenPOWER code generator
  • Write Once, Compile and Run Anywhere

“They way we have implemented this is to use PGI front end and PGI optimizer, and tie it into an LLVM back end code generator. We had support from IBM which has done a lot of work on LLVM and on the code generator and libraries. We were able to leverage a lot of that work,” said Wolfe

The current generation of IBM POWER chip is POWER8+, and Big Blue has said POWER9 processors will likely be ready sometime in 2017. Wolfe isn’t expecting major compatibility issues for the OpenACC compiler.

“Micro-architecturally I’m sure there will be difference in gates and layout and logic design, but from in instruction set perspective I don’t know how much difference [well see]. Typically it’s just additions, new instructions for behavior. Intel does things like double the length of the SIMD (single instruction, multiple data) register. I don’t know if IBM has plans for that.

“There will be versions of POWER8 with the CAPI interface and we’ll be able to work with NVLINK and I think that will be in all the POWER9s. Will it be compatible and will it be optimized for it is the other questions. The thing that we would hope is for the most part that the LLVM code generator will have the low level optimizing for that,” Wolfe said.

OpenACC.OpenPOWER Support

The additions of the University of Illinois, Brookhaven, and Stony Brook demonstrate the growing traction of OpenACC said Duncan Poole, director of strategic alliance for the accelerated computing group at NVIDIA and OpenACC president. He noted the value of OpenACC’s various training events (hackathons, workshops, etc) as an important force in attracting new members and sometimes presenting opportunities for computer scientists to publish their work.

“A hackathon that ran at the NCSA (National Center for Supercomputer Applications) brought the University of Illinois into to the fold. Brookhaven participated in a separate hackathon – it’s known for expertise in QCD (quantum chromodynamics) and has a particular library, Grid QCD, which is C++ code. C++ tends to stress the directives model of compilers so having them involved, providing feedback to us as to how we should change the standard and working with them to help migrate their code to OpenACC was important. They see the value and we see the value,” said Poole.

“UIUC joined OpenACC to support two key grants and projects from the NSF/NCSA and DOE that involve scientific research using complex, un-optimized code,” said John Larson, research scientist at the University of Illinois, Urbana-Champaign. “Being a member of the OpenACC standard organization will give both projects early access to technical features of the developing OpenACC language and also enable input that may influence new OpenACC language features.”

OpenACC has held five events in the last 14 months. Three more OpenACC hackathons are planned for the second half of 2016 at the Swiss Supercomputing Center (CSCS), CSC in Helsinki, Finland and the Oak Ridge National Lab. Hackathons are intensive five day hands-on coding sessions intended to help scientists parallelize their applications to run on accelerators and multi- core processors.

In the hackathons, teams (2-6 persons) are paired with experts from OpenACC community. “Very significantly that includes a compiler engineer. The immediate benefit from this is when you run into problems, the [first] thing that the developer asks is, “is it my code that caused the problem or something else.” Early on there were lots of bugs in the compiler but more recently, that hasn’t been the issue, it’s been more understanding the steps you take parallelize code,” said Poole

The first two steps, which Poole said they prefer teams have done before the hackathon, are to settle on their particular compiler of choice and to profile the code to identify where the opportunities for speed-up are. “But it’s not always the case. You basically go through the act of inserting directives to make your code parallel and the next step would be to insert the data directives that help describe data movement between host and the accelerator.”

The events are not designed to “ram OpenACC down everybody’s throat. Even in the hackathon it’s much more a use whatever tool is most appropriate to move your code forward. So it could be math libraries, it could be CUDA, OpenACC, OpenCL, whatever makes sense to the developer,” said Poole.

Poole agrees the term workshop is often used broadly. OpenACC has a fairly specific view of its events: training courses (~two days); workshops (~three days); hackathons (~four days); and academic workshops (~5 days). They vary in scale and duration (see list of upcoming events below).

Academic workshops are the most rigorous. “We do two of these a year right now. The one at ISC this year – (International Workshop on Performance Portable Programming Models for Accelerators (P3MA) with keynoter Simon Hammond of Sandia) – is an academic event: you submit your proposal for the paper you want to have published; it’s peer reviewed by other academics; the top one are selected and presented at the workshop. It’s a proper opportunity to publish for computer scientists,” said Poole

OpenACC Hackathons

Given the rapid change in the accelerator and processor landscape Poole and Wolfe agree significant challenges remain in efforts to parallelize code and enhance performance and portability. Wolf noted three ongoing issues.

General cleanup is one. “To be frank, the people who wrote the spec, and I mean me and others, don’t really write specifications for a living. We write what we think is correct but sometimes you are not quite as precise as you need be. Sometimes it’s an error but sometimes it’s an assumption that the person reading doesn’t have assumption in mind. So there’s some things in here about the way things are specified – one would be the reduction clause and whether it’s a data clause or not. In OpenACC, it’s not with the data clauses but it has some of the behavior of a data clauses so there’s some clean up that we need to make sure we have things specified properly,” he said.

Multiple device support is the second and one of the bigger headaches, said Wolfe. “Mateo Swiss, for example, bought a system where every node has got a dual socket Haswell (Intel) and eight K80s (see HPCwire article, Europe’s Fastest Supercomputer to get Pascal GPU Upgrade). How do you take advantage of that in a language like OpenACC where you really just want to say here’s a parallel loop, run it across all my resources. That’s a challenge on systems with separate memories. How are you going to manage the memory coherence and allocation with the data computation and data memory? How will you keep the K80s fed.”

Deep Memory is another difficult bottleneck. “If you have deep dynamic structures, multiply linked and nested with their data structures, and you want to move the whole structure over to the device, that’s a specific situation where you have got system memory and device memory and move data from one to the other. We have several different memory pools with different characteristics. With Xeon Phi, for example, you’ve got system memory and multichannel DRAM, high bandwidth memory. Some of these nodes are going to have you system memory in NVRAM and we don’t know quite what the characteristics of that will be but the plan I’m seeing is that it’s byte addressable,” said Wolfe.

“I’ve seen slides – but no circuit design – showing an AMD design where they have APU and CPU cores on chip and multiple types of memory attached – large system memory and a smaller high bandwidth memory – and all of these memories are exposed. They are not managed by the system, not managed by the hardware like a cache; it’s managed by the application. Were trying to see whether and how to manage this in the runtime [by] putting in some data directive that specifies characteristics of the program. I think it’s going to be a significant challenge because we never had a lot of experience with that. It’s not just changing he way you express parallelism, now it changing the memory management as well,” he said.

Challenges aside, OpenACC is working and working well say both Wolfe and Poole. As part of the announcement today, OpenACC cites a 2.5X speedup and significant power reduction on NekCEM (Nekton for Computational Electromagnetics) code achieved at Argonne Leadership Computing Facility.

OpenACC.NekCEM

[i] https://en.wikipedia.org/wiki/OpenACC

Subscribe to HPCwire's Weekly Update!

Be the most informed person in the room! Stay ahead of the tech trends with industy updates delivered to you every week!

What’s New in Computing vs. COVID-19: Fugaku, Congress, De Novo Design & More

July 2, 2020

Supercomputing, big data and artificial intelligence are crucial tools in the fight against the coronavirus pandemic. Around the world, researchers, corporations and governments are urgently devoting their computing reso Read more…

By Oliver Peckham

OpenPOWER Reboot – New Director, New Silicon Partners, Leveraging Linux Foundation Connections

July 2, 2020

Earlier this week the OpenPOWER Foundation announced the contribution of IBM’s A21 Power processor core design to the open source community. Roughly this time last year, IBM announced open sourcing its Power instructio Read more…

By John Russell

HPC Career Notes: July 2020 Edition

July 1, 2020

In this monthly feature, we'll keep you up-to-date on the latest career developments for individuals in the high-performance computing community. Whether it's a promotion, new company hire, or even an accolade, we've got Read more…

By Mariana Iriarte

Supercomputers Enable Radical, Promising New COVID-19 Drug Development Approach

July 1, 2020

Around the world, innumerable supercomputers are sifting through billions of molecules in a desperate search for a viable therapeutic to treat COVID-19. Those molecules are pulled from enormous databases of known compoun Read more…

By Oliver Peckham

HPC-Powered Simulations Reveal a Looming Climatic Threat to Vital Monsoon Seasons

June 30, 2020

As June draws to a close, eyes are turning to the latter half of the year – and with it, the monsoon and hurricane seasons that can prove vital or devastating for many of the world’s coastal communities. Now, climate Read more…

By Oliver Peckham

AWS Solution Channel

Maxar Builds HPC on AWS to Deliver Forecasts 58% Faster Than Weather Supercomputer

When weather threatens drilling rigs, refineries, and other energy facilities, oil and gas companies want to move fast to protect personnel and equipment. And for firms that trade commodity shares in oil, precious metals, crops, and livestock, the weather can significantly impact their buy-sell decisions. Read more…

Intel® HPC + AI Pavilion

Supercomputing the Pandemic: Scientific Community Tackles COVID-19 from Multiple Perspectives

Since their inception, supercomputers have taken on the biggest, most complex, and most data-intensive computing challenges—from confirming Einstein’s theories about gravitational waves to predicting the impacts of climate change. Read more…

Hyperion Forecast – Headwinds in 2020 Won’t Stifle Cloud HPC Adoption or Arm’s Rise

June 30, 2020

The semiannual taking of HPC’s pulse by Hyperion Research – late fall at SC and early summer at ISC – is a much-watched indicator of things come. This year is no different though the conversion of ISC to a digital Read more…

By John Russell

OpenPOWER Reboot – New Director, New Silicon Partners, Leveraging Linux Foundation Connections

July 2, 2020

Earlier this week the OpenPOWER Foundation announced the contribution of IBM’s A21 Power processor core design to the open source community. Roughly this time Read more…

By John Russell

Hyperion Forecast – Headwinds in 2020 Won’t Stifle Cloud HPC Adoption or Arm’s Rise

June 30, 2020

The semiannual taking of HPC’s pulse by Hyperion Research – late fall at SC and early summer at ISC – is a much-watched indicator of things come. This yea Read more…

By John Russell

Racism and HPC: a Special Podcast

June 29, 2020

Promoting greater diversity in HPC is a much-discussed goal and ostensibly a long-sought goal in HPC. Yet it seems clear HPC is far from achieving this goal. Re Read more…

Top500 Trends: Movement on Top, but Record Low Turnover

June 25, 2020

The 55th installment of the Top500 list saw strong activity in the leadership segment with four new systems in the top ten and a crowning achievement from the f Read more…

By Tiffany Trader

ISC 2020 Keynote: Hope for the Future, Praise for Fugaku and HPC’s Pandemic Response

June 24, 2020

In stark contrast to past years Thomas Sterling’s ISC20 keynote today struck a more somber note with the COVID-19 pandemic as the central character in Sterling’s annual review of worldwide trends in HPC. Better known for his engaging manner and occasional willingness to poke prickly egos, Sterling instead strode through the numbing statistics associated... Read more…

By John Russell

ISC 2020’s Student Cluster Competition Winners Announced

June 24, 2020

Normally, the Student Cluster Competition involves teams of students building real computing clusters on the show floors of major supercomputer conferences and Read more…

By Oliver Peckham

Hoefler’s Whirlwind ISC20 Virtual Tour of ML Trends in 9 Slides

June 23, 2020

The ISC20 experience this year via livestreaming and pre-recordings is interesting and perhaps a bit odd. That said presenters’ efforts to condense their comments makes for economic use of your time. Torsten Hoefler’s whirlwind 12-minute tour of ML is a great example. Hoefler, leader of the planned ISC20 Machine Learning... Read more…

By John Russell

At ISC, the Fight Against COVID-19 Took the Stage – and Yes, Fugaku Was There

June 23, 2020

With over nine million infected and nearly half a million dead, the COVID-19 pandemic has seized the world’s attention for several months. It has also dominat Read more…

By Oliver Peckham

Supercomputer Modeling Tests How COVID-19 Spreads in Grocery Stores

April 8, 2020

In the COVID-19 era, many people are treating simple activities like getting gas or groceries with caution as they try to heed social distancing mandates and protect their own health. Still, significant uncertainty surrounds the relative risk of different activities, and conflicting information is prevalent. A team of Finnish researchers set out to address some of these uncertainties by... Read more…

By Oliver Peckham

[email protected] Turns Its Massive Crowdsourced Computer Network Against COVID-19

March 16, 2020

For gamers, fighting against a global crisis is usually pure fantasy – but now, it’s looking more like a reality. As supercomputers around the world spin up Read more…

By Oliver Peckham

[email protected] Rallies a Legion of Computers Against the Coronavirus

March 24, 2020

Last week, we highlighted [email protected], a massive, crowdsourced computer network that has turned its resources against the coronavirus pandemic sweeping the globe – but [email protected] isn’t the only game in town. The internet is buzzing with crowdsourced computing... Read more…

By Oliver Peckham

Global Supercomputing Is Mobilizing Against COVID-19

March 12, 2020

Tech has been taking some heavy losses from the coronavirus pandemic. Global supply chains have been disrupted, virtually every major tech conference taking place over the next few months has been canceled... Read more…

By Oliver Peckham

Supercomputer Simulations Reveal the Fate of the Neanderthals

May 25, 2020

For hundreds of thousands of years, neanderthals roamed the planet, eventually (almost 50,000 years ago) giving way to homo sapiens, which quickly became the do Read more…

By Oliver Peckham

DoE Expands on Role of COVID-19 Supercomputing Consortium

March 25, 2020

After announcing the launch of the COVID-19 High Performance Computing Consortium on Sunday, the Department of Energy yesterday provided more details on its sco Read more…

By John Russell

Steve Scott Lays Out HPE-Cray Blended Product Roadmap

March 11, 2020

Last week, the day before the El Capitan processor disclosures were made at HPE's new headquarters in San Jose, Steve Scott (CTO for HPC & AI at HPE, and former Cray CTO) was on-hand at the Rice Oil & Gas HPC conference in Houston. He was there to discuss the HPE-Cray transition and blended roadmap, as well as his favorite topic, Cray's eighth-gen networking technology, Slingshot. Read more…

By Tiffany Trader

Honeywell’s Big Bet on Trapped Ion Quantum Computing

April 7, 2020

Honeywell doesn’t spring to mind when thinking of quantum computing pioneers, but a decade ago the high-tech conglomerate better known for its control systems waded deliberately into the then calmer quantum computing (QC) waters. Fast forward to March when Honeywell announced plans to introduce an ion trap-based quantum computer whose ‘performance’ would... Read more…

By John Russell

Leading Solution Providers

Contributors

Neocortex Will Be First-of-Its-Kind 800,000-Core AI Supercomputer

June 9, 2020

Pittsburgh Supercomputing Center (PSC - a joint research organization of Carnegie Mellon University and the University of Pittsburgh) has won a $5 million award Read more…

By Tiffany Trader

‘Billion Molecules Against COVID-19’ Challenge to Launch with Massive Supercomputing Support

April 22, 2020

Around the world, supercomputing centers have spun up and opened their doors for COVID-19 research in what may be the most unified supercomputing effort in hist Read more…

By Oliver Peckham

Australian Researchers Break All-Time Internet Speed Record

May 26, 2020

If you’ve been stuck at home for the last few months, you’ve probably become more attuned to the quality (or lack thereof) of your internet connection. Even Read more…

By Oliver Peckham

15 Slides on Programming Aurora and Exascale Systems

May 7, 2020

Sometime in 2021, Aurora, the first planned U.S. exascale system, is scheduled to be fired up at Argonne National Laboratory. Cray (now HPE) and Intel are the k Read more…

By John Russell

Nvidia’s Ampere A100 GPU: Up to 2.5X the HPC, 20X the AI

May 14, 2020

Nvidia's first Ampere-based graphics card, the A100 GPU, packs a whopping 54 billion transistors on 826mm2 of silicon, making it the world's largest seven-nanom Read more…

By Tiffany Trader

10nm, 7nm, 5nm…. Should the Chip Nanometer Metric Be Replaced?

June 1, 2020

The biggest cool factor in server chips is the nanometer. AMD beating Intel to a CPU built on a 7nm process node* – with 5nm and 3nm on the way – has been i Read more…

By Doug Black

Summit Supercomputer is Already Making its Mark on Science

September 20, 2018

Summit, now the fastest supercomputer in the world, is quickly making its mark in science – five of the six finalists just announced for the prestigious 2018 Read more…

By John Russell

TACC Supercomputers Run Simulations Illuminating COVID-19, DNA Replication

March 19, 2020

As supercomputers around the world spin up to combat the coronavirus, the Texas Advanced Computing Center (TACC) is announcing results that may help to illumina Read more…

By Staff report

  • arrow
  • Click Here for More Headlines
  • arrow
Do NOT follow this link or you will be banned from the site!
Share This