News Supermassive Black Hole Consumed 100 Million CPU Hours

There are typos in the article "All of this is a cool 55 million light-years from Earth." Sagittarius A* is only 25,640 light years from Earth. You have put in 2000x the distance in the article. The distance to the supermassive black hole in the middle of M87*, imaged in 2019, is ~55 million light years.

"Frontera leverages 448,448 CPU cores courtesy of 16,016 units of Intel's Xeon Platinum 8280 chips, a Broadwell-class CPU leveraging 28 Intel cores running at 2.7GHz." Frontera uses Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz Number of cores: 16 per socket, 32 per node
https://www.tacc.utexas.edu/systems/frontera
 

Giroro

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What is a CPU hour? I have no context as to what amount of work that is.
Is that calculated per core, thread, or socket? How do you normalize between CPUs with wildy different performance?

How many CPU hours can, say, a Ryzen 9 5950x work in 1 hour?
 
What is a CPU hour? I have no context as to what amount of work that is.
Is that calculated per core, thread, or socket? How do you normalize between CPUs with wildy different performance?

How many CPU hours can, say, a Ryzen 9 5950x work in 1 hour?
It just means using one CPU for one hour. We could probably assume a CPU is a core since when doing CPU bound work, a core is basically another CPU. It's a similar metric as man-hour, which is literally one person working for one hour. The actual time to completion doesn't matter and performance is ignored, you simply adjust the amount of time you think you'll need if the performance is actually better or worse than some baseline you're using. For instance if you estimate 10 CPU hours of work to get something done, you can get it done in 2 hours by scheduling 5 CPUs to do the work. Or if you're running on higher performing machines than when you made the estimate, you could reduce this to 8 CPU hours.

So basically, it's just saying they spent a cumulative total of 100 million hours crunching numbers.

EDIT: I realized this doesn't really explain why things are measured this way. The basic reason for all of this is simple: running stuff on a HPC, server, etc, is billed by the time you use it. HPCs and the like are typically time shared, the researchers don't own any of the computers that do the heavy lifting, so to speak. So for the purposes of accounting, you have to estimate how many hours you think you'll need on a system to do the work. Then the bean counters and proposal people can go "okay, we need $XXXX for compute costs"
 
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There are typos in the article "All of this is a cool 55 million light-years from Earth." Sagittarius A* is only 25,640 light years from Earth. You have put in 2000x the distance in the article. The distance to the supermassive black hole in the middle of M87*, imaged in 2019, is ~55 million light years.

"Frontera leverages 448,448 CPU cores courtesy of 16,016 units of Intel's Xeon Platinum 8280 chips, a Broadwell-class CPU leveraging 28 Intel cores running at 2.7GHz." Frontera uses Intel(R) Xeon(R) CPU E5-2620 v4 @ 2.10GHz Number of cores: 16 per socket, 32 per node
https://www.tacc.utexas.edu/systems/frontera
It's not just typos...
"... comparably minute amount of light that actually manages to escape its event horizon..."
Apparently whoever wrote this article doesn't understand how black holes work either. It would have taken 10 minutes to educate themself about how the photo is taken and what's actually in it, but rather than that they just make up something wildly incorrect.
 
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thisisaname

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It's not just typos...
"... comparably minute amount of light that actually manages to escape its event horizon..."
Apparently whoever wrote this article doesn't understand how black holes work either. It would have taken 10 minutes to educate themself about how the photo is taken and what's actually in it, but rather than that they just make up something wildly incorrect.
No light escapes the event horizon, it is why it is called a black hole.

The light we see and it is quite bright but very very far away is from matter that orbits around the black hole (out side the event horizon) that has been accelerated to close to the speed of light.

So a black hole is both very dark and very bright!
 

Giroro

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It just means using one CPU for one hour. We could probably assume a CPU is a core since when doing CPU bound work, a core is basically another CPU. It's a similar metric as man-hour, which is literally one person working for one hour. The actual time to completion doesn't matter and performance is ignored, you simply adjust the amount of time you think you'll need if the performance is actually better or worse than some baseline you're using. For instance if you estimate 10 CPU hours of work to get something done, you can get it done in 2 hours by scheduling 5 CPUs to do the work. Or if you're running on higher performing machines than when you made the estimate, you could reduce this to 8 CPU hours.

So basically, it's just saying they spent a cumulative total of 100 million hours crunching numbers.

EDIT: I realized this doesn't really explain why things are measured this way. The basic reason for all of this is simple: running stuff on a HPC, server, etc, is billed by the time you use it. HPCs and the like are typically time shared, the researchers don't own any of the computers that do the heavy lifting, so to speak. So for the purposes of accounting, you have to estimate how many hours you think you'll need on a system to do the work. Then the bean counters and proposal people can go "okay, we need $XXXX for compute costs"
So, spread over ~450,000 cores, what this article is really saying is that all that math only actually took about 10 days? And that it probably would have gone a lot faster if they had been using newer CPUs?
 
I just ran a relative numbers comparison we can all associate with on scale based on a grain of sand (using .33mm diameter grain). If our sun were a grain of sand, this black hole would be 4,333ft in diameter or about .82 miles (or 1320 meters or about 1.3 kilometers). That's a big freaking hole!
 

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