In Australia, HPC Illuminates the Early Universe

By Oliver Peckham

May 11, 2020

Many billions of years ago, the universe was a swirling pool of gas. Unraveling the story of how we got from there to here isn’t an easy task, with many simulations of large swaths of the universe taking years to complete on powerful supercomputers. In a talk for the ICM Seminars series (hosted by the Interdisciplinary Centre for Mathematical and Computational Modelling University of Warsaw), Dr. Simon Mutch highlighted how Australian research organizations are working around the computational requirements to deliver insights into the origins of the universe as we know it.

Dr. Simon Mutch

The reionization of the universe – and why we should care about it

“Immediately after the Big Bang, the universe was filled mostly just with neutral hydrogen – there wasn’t really much else there,” said Mutch, who is a postdoctoral fellow at the University of Melbourne’s ASTRO 3D Centre of Excellence and a senior research data specialist for the Melbourne Data Analytics Platform. “But then there were gravitational perturbations that caused gas to collapse in on itself, and eventually stars and galaxies began to form, and those stars gave out light, which was of high enough energy to start to ionize the surrounding neutral gas, so it stripped electrons off that neutral gas and changed its properties.”

This ionization, he explained, spread into bubbles, and as galaxies grew in number and size, the bubbles began to overlap, eventually resulting in the total reionization of the universe – some 12.5 billion years ago. The relationship between these ionized bubbles and the galaxies that birthed them a major focus for Mutch and his colleagues. 

Over the course of billions of years, ionization bubbles grew to fill the entire universe. Image courtesy of Simon Mutch.

 “That’s really interesting, because it means that if we can observe this reionization signal … then we can infer something about the galaxies which are driving this reionization process.” Mutch said. “What’s even more interesting is that the reionization signal is sensitive to all galaxies.” In terms of the galaxies populating the universe, he explained, relatively faint galaxies are the most common – but also the most difficult to see. “By studying this reionization structure,” he said, “we can actually learn something about the very smallest, very faintest galaxies that we can’t actually see.” 

Mutch compared the process to dropping stones in a pond and studying the ripples to understand the shapes and sizes of each stone. “The main problem is: how do we connect the properties of galaxies to the signature of the bubbles that we see during reionization?” he said. “For that, we use cosmological simulations.”

The trouble with simulations

Cosmological simulations of galaxy formation build a chunk of the universe from the ground up, accounting for elements like gravity, dark matter, heating, cooling, turbulence, chemistry, supernovae, black holes, magnetic fields and more, which are all woven into hydrodynamical or mesh models.

“While these are incredibly powerful, they are extremely computationally intensive,” Mutch said. “That’s because there is a large dynamic range, both in terms of temporal and spatial resolution.” By way of examples, he discussed IllustrisTNG, a galaxy formation simulation one billion light years across that required 35 million CPU hours on the Hazel Hen supercomputer at the High Performance Computing Center (HLRS) in Stuttgart. Similarly, he said, the larger BlueTides simulation took 20 million CPU hours on the Blue Waters system at NCSA, nearly taking up the entire machine.

The necessary scale of simulating reionization compounded the high computational needs. “What we’re always doing is making this tradeoff between the amount of resolution we get in the simulation and the size of the simulation,” Mutch said. “This problem is particularly acute, though, if you’re talking about the early universe and reionization.” The reionization bubbles were tens of millions of light years across, so in order to produce a statistically relevant sample of them, you would need many bubbles – and a massive simulation.

Normally, researchers adjust parameters so they can match to the known universe nearby. But not much is known about the early universe – so instead, Mutch and his colleagues needed to run “many, many different realizations of the simulations” to test different models, feedback processes and other variables to see how they affected the ionized bubbles.

Finding a path through the cosmos

Tackling this uphill battle was the goal for the University of Melbourne’s Dark-ages, Reionization And Galaxy-formation Observables Numerical Simulation, or “DRAGONS,” program. (“We love our acronyms in astronomy,” Mutch said. “Everything needs to have a good acronym.”)

Thankfully, he said, the universe gave them a helping hand. Overall, the universe consists of around 70% dark energy, 25% dark matter and only 5% normal matter – what we interact with in our daily lives. “What this actually means is that we can do a pretty good job of simulating the position and the large-scale distribution of the matter by simply ignoring normal matter, and that makes things much easier,” Mutch said, explaining that they could ignore gas, shocks, star formation and more. “All we care about is getting the large-scale distribution of matter correct.”

The matter composition of the universe. Image courtesy of Simon Mutch.

So the researchers developed a N-body (particle) simulation that treated all the matter in the universe as collisionless. “We can pour all our computing power into doing this problem of gravity, essentially, and doing as big a simulation to as high a resolution as we possibly can,” Mutch said. They ran a large N-body simulation – about 300 million light years on each side – with billions of particles, each corresponding to a mass about 400 million times that of the sun.

The telltale “knots” circled in the N-body simulation. Image courtesy of Simon Mutch.

Looking at the simulation, the researchers then identified “knots” in the images – formations called “dark matter halos” where galaxies would start to form. The researchers tracked these halos through the simulation, building hierarchical merger trees that described how the halos coalesced over time. Using a semi-analytic galaxy formation model, they then “painted on” galaxies over the halos. 

“What we also did, which was unique at the time with the DRAGONS program,” Mutch said, “is that we use the information of these galaxies to calculate how many ionizing photons they were producing and then fed that into another code, called a seminumerical model, that then was able to give us what the ionization state of the volume was a function of position. So basically, it allowed us to figure out where these ionized bubbles were.”

With that process in hand, the researchers would then evolve the galaxies again, run the seminumerical model again to get the ionization results and repeat the process until the ionization was complete.

The computational implications

“What this allows us to do is to run one really expensive N-body simulation, on the order of tens or hundreds of millions of CPU hours, and just do that once,” Mutch explained. “And then we can keep running our semi-analytic model over the top of that.” The semi-analytic model, he said, took only on the order of ten CPU hours. “And that’s where things start to get really powerful.”

“What that means is we’re no longer restricted to running one really big cosmological hydrodynamic simulation once every few years and needing a large grant and a whole supercomputer to do it,” Mutch said. “Instead, we can start to explore what happens when we change different parameters in our galaxy model, and we can then see how that changes the signal from reionization.”

This capacity for rapid iteration leaves the researchers well-positioned to be able to interpret ionization results as near-future high-power telescopes like the Square Kilometre Array (which is under construction in South Africa and Australia) begin to provide large amounts of data on the radio signals produced by reionization. “So that way, when we measure the ionized bubbles,” Mutch said, “we can infer something about the galaxies.”

Mutch is also taking part in the Genesis simulations under the government-funded ASTRO 3D program. The 30 researchers under Genesis are preparing to run a “big box” simulation – half a billion light years on each side – with 80003 particles inside of it. They expect the model to be “competitive on an international scale,” Mutch said.

To conduct the reionization simulations and the Genesis simulations, Mutch and his colleagues turned to homegrown supercomputing power. Initially, they were using NCI Australia’s Raijin supercomputer, an Intel-based system delivering 1.7 Linpack petaflops that barely squeaked into the most recent Top500 list. Raijin, however, is now being decommissioned, and the researchers are helping to stress test its replacement: Gadi. 

The Gadi supercomputer. Image courtesy of NCI.

While not yet complete, Gadi will boast 3,000 Cascade Lake nodes with two 24-core CPUs and 192 GB of memory, 160 nodes with four Nvidia V100 GPUs and 50 large memory nodes with 1.5 TB of memory. Already, Gadi’s first phase – installed in 2019 – is delivering 4.4 Linpack petaflops, placing it 47th in its first appearance on the Top500 list.

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!

ISC21 Cluster Competition Bracketology

June 18, 2021

For the first time ever, cluster competition experts have gathered together for an actual seeding reveal for the ISC21 Student Cluster Competition. What’s this, you ask? It’s where bona fide student cluster competi Read more…

OSC Enables On-Demand HPC for Automotive Engineering Firm

June 18, 2021

In motorsports, vehicle designers are constantly looking for the tiniest sliver of time to shave off through some clever piece of engineering – but as the low-hanging fruit gets snatched up, those advances are getting Read more…

PNNL Researchers Unveil Tool to Accelerate CGRA Development

June 18, 2021

Moore’s law is in decline due to the physical limits of transistor chips, putting an expiration date on a hitherto-perennial exponential trend in computing power – and leaving hardware developers scrambling to contin Read more…

TU Wien Announces VSC-5, Austria’s Most Powerful Supercomputer

June 17, 2021

Austria is getting a new top supercomputer: VSC-5, the latest iteration of the Vienna Scientific Cluster. The news was announced by VSC-5’s soon-to-be home, TU Wien (also known as the Vienna University of Technology). Read more…

Supercomputing Helps Advance Hydrogen Energy Research

June 16, 2021

Hydrogen energy has long remained an elusive target of the renewable energy industry, promising clean, carbon-free energy that would allow for rapid refueling, unlike current battery-based electric vehicles. Hydrogen-bas Read more…

AWS Solution Channel

Accelerating research and development for new medical treatments

Today, more than 290,000 researchers in France are working to provide better support and care for patients through modern medical treatment. To fulfill their mission, these researchers must be equipped with powerful tools. Read more…

FF4EuroHPC Initiative Highlights Results of First Open Call

June 16, 2021

EuroHPC is kicking into high gear, with seven of its first eight systems detailed – and one of them already operational. While the systems are, perhaps, the flashiest endeavor of the European Commission’s HPC effort, Read more…

TU Wien Announces VSC-5, Austria’s Most Powerful Supercomputer

June 17, 2021

Austria is getting a new top supercomputer: VSC-5, the latest iteration of the Vienna Scientific Cluster. The news was announced by VSC-5’s soon-to-be home, T Read more…

Catching up with ISC 2021 Digital Program Chair Martin Schulz

June 16, 2021

Leibniz Research Centre (LRZ)’s content creator Susanne Vieser interviews ISC 2021 Digital Program Chair, Prof. Martin Schulz to gain an understanding of his ISC affiliation, which is outside his usual scope of work at the research center and the Technical University of Munich. Read more…

Intel Debuts ‘Infrastructure Processing Unit’ as Part of Broader XPU Strategy

June 15, 2021

To boost the performance of busy CPUs hosted by cloud service providers, Intel Corp. has launched a new line of Infrastructure Processing Units (IPUs) that take Read more…

ISC Keynote: Glimpse into Microsoft’s View of the Quantum Computing Landscape

June 15, 2021

Looking for a dose of reality and realistic optimism about quantum computing? Matthias Troyer, Microsoft distinguished scientist, plans to do just that in his ISC2021 keynote in two weeks – Quantum Computing: From Academic Research to Real-world Applications. He notes wryly that classical... Read more…

A Carbon Crisis Looms Over Supercomputing. How Do We Stop It?

June 11, 2021

Supercomputing is extraordinarily power-hungry, with many of the top systems measuring their peak demand in the megawatts due to powerful processors and their c Read more…

Honeywell Quantum and Cambridge Quantum Plan to Merge; More to Follow?

June 10, 2021

Earlier this week, Honeywell announced plans to merge its quantum computing business, Honeywell Quantum Solutions (HQS), which focuses on trapped ion hardware, Read more…

ISC21 Keynoter Xiaoxiang Zhu to Deliver a Bird’s-Eye View of a Changing World

June 10, 2021

ISC High Performance 2021 – once again virtual due to the ongoing pandemic – is swiftly approaching. In contrast to last year’s conference, which canceled Read more…

Xilinx Expands Versal Chip Family With 7 New Versal AI Edge Chips

June 10, 2021

FPGA chip vendor Xilinx has been busy over the last several years cranking out its Versal AI Core, Versal Premium and Versal Prime chip families to fill customer compute needs in the cloud, datacenters, networks and more. Now Xilinx is expanding its reach to the booming edge... Read more…

AMD Chipmaker TSMC to Use AMD Chips for Chipmaking

May 8, 2021

TSMC has tapped AMD to support its major manufacturing and R&D workloads. AMD will provide its Epyc Rome 7702P CPUs – with 64 cores operating at a base cl Read more…

Intel Launches 10nm ‘Ice Lake’ Datacenter CPU with Up to 40 Cores

April 6, 2021

The wait is over. Today Intel officially launched its 10nm datacenter CPU, the third-generation Intel Xeon Scalable processor, codenamed Ice Lake. With up to 40 Read more…

Berkeley Lab Debuts Perlmutter, World’s Fastest AI Supercomputer

May 27, 2021

A ribbon-cutting ceremony held virtually at Berkeley Lab's National Energy Research Scientific Computing Center (NERSC) today marked the official launch of Perlmutter – aka NERSC-9 – the GPU-accelerated supercomputer built by HPE in partnership with Nvidia and AMD. Read more…

Google Launches TPU v4 AI Chips

May 20, 2021

Google CEO Sundar Pichai spoke for only one minute and 42 seconds about the company’s latest TPU v4 Tensor Processing Units during his keynote at the Google I Read more…

CERN Is Betting Big on Exascale

April 1, 2021

The European Organization for Nuclear Research (CERN) involves 23 countries, 15,000 researchers, billions of dollars a year, and the biggest machine in the worl Read more…

Iran Gains HPC Capabilities with Launch of ‘Simorgh’ Supercomputer

May 18, 2021

Iran is said to be developing domestic supercomputing technology to advance the processing of scientific, economic, political and military data, and to strengthen the nation’s position in the age of AI and big data. On Sunday, Iran unveiled the Simorgh supercomputer, which will deliver.... Read more…

HPE Launches Storage Line Loaded with IBM’s Spectrum Scale File System

April 6, 2021

HPE today launched a new family of storage solutions bundled with IBM’s Spectrum Scale Erasure Code Edition parallel file system (description below) and featu Read more…

Quantum Computer Start-up IonQ Plans IPO via SPAC

March 8, 2021

IonQ, a Maryland-based quantum computing start-up working with ion trap technology, plans to go public via a Special Purpose Acquisition Company (SPAC) merger a Read more…

Leading Solution Providers


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…

AMD Launches Epyc ‘Milan’ with 19 SKUs for HPC, Enterprise and Hyperscale

March 15, 2021

At a virtual launch event held today (Monday), AMD revealed its third-generation Epyc “Milan” CPU lineup: a set of 19 SKUs -- including the flagship 64-core, 280-watt 7763 part --  aimed at HPC, enterprise and cloud workloads. Notably, the third-gen Epyc Milan chips achieve 19 percent... Read more…

Julia Update: Adoption Keeps Climbing; Is It a Python Challenger?

January 13, 2021

The rapid adoption of Julia, the open source, high level programing language with roots at MIT, shows no sign of slowing according to data from I Read more…

Can Deep Learning Replace Numerical Weather Prediction?

March 3, 2021

Numerical weather prediction (NWP) is a mainstay of supercomputing. Some of the first applications of the first supercomputers dealt with climate modeling, and Read more…

GTC21: Nvidia Launches cuQuantum; Dips a Toe in Quantum Computing

April 13, 2021

Yesterday Nvidia officially dipped a toe into quantum computing with the launch of cuQuantum SDK, a development platform for simulating quantum circuits on GPU-accelerated systems. As Nvidia CEO Jensen Huang emphasized in his keynote, Nvidia doesn’t plan to build... Read more…

Microsoft to Provide World’s Most Powerful Weather & Climate Supercomputer for UK’s Met Office

April 22, 2021

More than 14 months ago, the UK government announced plans to invest £1.2 billion ($1.56 billion) into weather and climate supercomputing, including procuremen Read more…

African Supercomputing Center Inaugurates ‘Toubkal,’ Most Powerful Supercomputer on the Continent

February 25, 2021

Historically, Africa hasn’t exactly been synonymous with supercomputing. There are only a handful of supercomputers on the continent, with few ranking on the Read more…

The History of Supercomputing vs. COVID-19

March 9, 2021

The COVID-19 pandemic poses a greater challenge to the high-performance computing community than any before. HPCwire's coverage of the supercomputing response t Read more…

  • arrow
  • Click Here for More Headlines
  • arrow