22 Years Of Supercomputer Evolution

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bit_user

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SW26010 is basically a rip-off of the Cell architecture that everyone hated programming so much that it never had a successor.

It might get fast Linpack benchies, but I don't know how much else will run fast on it. I'd be surprised if they didn't have a whole team of programmers just to optimize Linpack for it.

I suspect Sunway TaihuLight was done mostly for bragging rights, as opposed to maximizing usable performance. On the bright side, I'm glad they put emphasis on power savings and efficiency.
 

bit_user

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BTW, nowhere in the article you linked does it support your claim that:
the U.S. government restricted the sale of server-grade Intel processors in China in an attempt to give the U.S. time to build a new supercomputer capable of surpassing the Tianhe-2.
 

bit_user

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aldaia only downvotes because I'm right. If I'm wrong, prove it.

Look, we all know China will eventually dominate all things. I'm just saying this thing doesn't pwn quite as the top line numbers would suggest. It's a lot of progress, nonetheless.

BTW, China's progress would be more impressive, if it weren't tainted by the untold amounts of industrial espionage. That makes it seem like they can only get ahead by cheating, even though I don't believe that's true.

And if they want to avoid future embargoes by the US, EU, and others, I'd recommend against such things as massive DDOS attacks on sites like github.
 

g00ey

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I'd assume that what "everyone" hated was to have to maintain software (i.e. games) for very different architectures. Maintaining a game for PS3, XBOX360 and PC that all have their own architecture apparently is more of a hurdle that if they all were Intel-based or whatever architecture have you. At least XboX360 had DirectX...

In the heydays of PowerPC, developers liked it better than the Intel architecture, particularly assembler developers. Today, it may not have that "fancy" stuff such as AVX, SSE etc but it probably is quite capable for computations. Benchmarks should be able to give some indications...
 

bit_user

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I'm curious how you got from developers hating Cell programming, to game companies preferring not to support different platforms, and why they would then single out the PS3 for criticism, when this problem was hardly new. This requires several conceptual leaps from my original statement, as well as assuming I have even more ignorance of the matter than you've demonstrated. I could say I'm insulted, but really I'm just annoyed.

No, you're way off base. Cell was painful to program, because the real horsepower is in the vector cores (so-called PPEs), but they don't have random access to memory. Instead, they have only a tiny bit of scratch pad RAM, and must DMA everything back and forth from main memory (or their neighbors). This means virtually all software for it must be effectively written from scratch and tuned to queue up work efficiently, so that the vector cores don't waste loads of time doing nothing while data is being copied around. Worse yet, many algorithms inherently depend on random access and perform poorly on such an architecture.

In terms of programming difficulty, the gap in complexity between it and multi-threaded programming is at least as big as that separating single-threaded and multi-threaded programming. And that assumes you're starting from a blank slate - not trying to port existing software to it. I think it's safe to say it's even harder than GPU programming, once you account for performance tuning.

Architectures like this are good at DSP, dense linear algebra, and not a whole lot else. The main reason they were able to make it work in a games console is because most game engines really aren't that different from each other and share common, underlying libraries. And as game engines and libraries became better tuned for it, the quality of PS3 games improved noticeably. But HPC is a different beast, which is probably why IBM never tried to follow it with any successors.

I'm not even sure what you're talking about, but I'd just point out that both Cell and the XBox 360's CPUs were derived from Power PC. And PPC did have AltiVec, which had some advantages over MMX & SSE.
 

alidan

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ah the cel... listening to devs talk about it and an mit lecture, the main problems with it were this
1) sony refused to give out proper documentation, they wanted their games to get progressively better as the console aged, preformance wise and graphically, so what better way then to kneecap devs
2) from what i understand about the architecture, and im not going to say this right, you had one core devoted to the os/drm, then you had the rest devoted to games and one core disabled on each to keep yields (something from the early day of the ps3) then you had to program the games while thinking of what core the crap executed on, all in all, a nightmare to work with.

if a game was made ps3 first it would port fairly good across consoles, but most games were made xbox first, and porting to ps3 was a nightmare.
 

bit_user

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It's slightly annoying that they took a 8 + 1 core CPU and turned it into a 6 + 1 core CPU, but I doubt anyone was too bothered about that.

I think PS4 launched with only 4 of the 8 cores available for games (or maybe it was 5/8?). Recently, they unlocked one more. I wonder how many the PS4 Neo will allow.

This is part of what I was saying. Again, the reason why it mattered which core was that the memory model was so restrictive. Each PPE plays in its own sandbox, and has to schedule any copies to/from other cores or main memory. Most multi-core CPUs don't work this way, as it's too much burden to place on software, with the biggest problem being that it prevents one from using any libraries that weren't written to work this way.

Now, if you write your software that way, you can port it to XBox 360/PC/etc. by simply taking the code that'd run on the PPEs and put it in a normal userspace thread. The DMA operations can be replaced with memcpy's (and, with a bit more care, you could even avoid some copying).

Putting it in more abstract terms, the Cell strictly enforces a high degree of data locality. Taking code written under that constraint and porting it to a less constrained architecture is easy. Going the other way is hard.
 

alidan

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as for turning cores off, that's largely to do with yields, later on in the consoles cycle they unlocked cores so some systems that weren't bad chips got slightly better performance in some games then other consoles, at least on ps3, that meant all of nothing as it had a powerful cpu but the gpu was bottlenecking it, opposite of the 360 where the cpu was bottlenecking that one at least if i remember the systems right.
 

bit_user

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Right. Did you actually check the link he cited? This had nothing to do with trying to hold China back, so that the US could catch up. That would indeed be childish.

Almost as childish as say... deciding to annex the South China Sea, and then ignoring the international tribunal that tells you it's illegal. Or, what about launching a massive and sustained attack on Github, to make it remove an opensource project you don't like? Or maybe hacking foreign journalists and outspoken critics of your country, and blocking your citizens from seeing any news sources that ever cast your country in a negative light?

Anyway, I think the reason they chose to target high-performance computing is probably that they thought it's one of the few areas left that could potentially hurt. Let's face it, the US doesn't really export a whole lot that China actually needs.
 
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