computer science

Gyoukou

Gyoukou is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Gyoukou rather than just read about it. In short: Gyoukou (Japanese: 暁光, Hepburn: gyōkō; dawn light) is a supercomputer developed by ExaScaler and PEZY Computing, based around ExaScaler's ZettaScaler immersion cooling system. It was deployed at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokohama Institute for Earth Sciences, the same floor where the Earth Simulator is located.

Key takeaways

Gyoukou belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gyoukou to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gyoukou from memory before moving on to harder problems.

Reference excerpt

Gyoukou (Japanese: 暁光, Hepburn: gyōkō; dawn light) is a supercomputer developed by ExaScaler and PEZY Computing, based around ExaScaler's ZettaScaler immersion cooling system. It was deployed at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokohama Institute for Earth Sciences, the same floor where the Earth Simulator is located. Amid the scandal regarding the development grant, it was removed from JAMSTEC in April 2018.

System

Gyoukou is based on ExaScaler's ZettaScaler-2.x technology which features liquid immersion cooling system using Fluorinert. Each immersion tank can contain 16 Bricks. A Brick consists of a backplane board, 32 PEZY-SC2 modules, 4 Intel Xeon D host processors, and 4 InfiniBand EDR cards. Modules inside a Brick are connected by hierarchical PCI Express fabric switches, and the Bricks are interconnected by InfiniBand. Each PEZY-SC2 module contains 2048 processing elements (1 GHz design), six MIPS64 control processors, and 4 DDR4 DIMMs (64GB per module as of November 2017).

Performance With partial configuration, Gyoukou was ranked 69th at 1,677.1 teraflops on the June 2017 TOP500 ranking. After upgrade to full scale (equivalent of 19.5 immersion tanks) using newer ZettaScaler-2.2 system, it ranked 4th at 19,135.8 teraflops on the November 2017 TOP500 ranking. At the time of benchmarking, 1984 out of 2048 cores of each PEZY-SC2 were used at 700 MHz clock. Gyoukou has high energy efficiency, and it ranked 5th at 14.173 gigaflops/watt on the November 2017 Green500 energy efficiency ranking. at the time benchmarked as 19,860,000 "cores" (after an upgrade).

Notes

External links

ExaScaler Inc. PEZY Computing K.K. Gyoukou Supercomputer leveraging 48V Factorized Power on YouTube

Illustrations

Worked examples

Example 1 — a first encounter with Gyoukou

Start with the simplest possible case. Write down what Gyoukou claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Gyoukou before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Gyoukou ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Gyoukou

In research: Gyoukou appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Gyoukou in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Gyoukou is common in secondary-school and first-year university syllabi. It links to neighbouring topics Japan Agency for Marine-Earth Science and Technology, Supercomputers, Supercomputing in Japan, so understanding it makes those chapters shorter.
In everyday life: Look for Gyoukou outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Gyoukou in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gyoukou means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Gyoukou out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gyoukou in simple terms?

Why does Gyoukou matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Gyoukou?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Gyoukou.