
Optalysys has 340-gigaflop optical computing system in works, exaflops to follow - msane
http://www.extremetech.com/extreme/187746-by-2020-you-could-have-an-exascale-speed-of-light-optical-computer-on-your-desk
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silentvoice
They are specifically targeting CFD applications, and so the cited FLOPs count
might be misleading (but I don't know enough about optical computing to say
for sure) I will comment on why I think this is so.

If this tool can perform very fast fourier transforms then it will benefit
many simulation codes which rely on an approximation technique known as
spectral approximation. In that case the huge FLOP/s count will only be
realized in "high orders," that is when these spectral methods are pushed to
their limits - in which case much existing research today breaks down and the
methods can simply become unusable by e.g. yielding a 'theoretically'
invertible matrix that has a numerically infinite condition number; no amount
of fourier transforms can dig you out of that hole. This problem is not fully
understood in the spectral method literature, and it rears its face in many
different ways depending on the problem context.

GPUs have a similar problem, their ability to churn out dense linear algebra
operations at high scale is so good that the vast majority of algorithms have
a huge memory bottleneck, not a FLOP/s bottleneck. The result is people rarely
see the insane promised 100X speedup of their simulation codes because they
rarely are one massive dense linear algebra operation such as a matrix-matrix
multiply, but rather a combination of small dense linear algebra ops + memory
bound operations like gathers and scatters. Ironically spectral methods also
work very well on the GPU in high orders, because they effectively replace
memory bound operations with dense linear algebra operations - which the GPU
eats for breakfast, but again: high orders -> still an unsolved area of
simulation mathematics; a lot of things happen which we don't have the answer
for and they frequently disrupt the method from being applicable.

As someone who uses spectral methods every day I would love to see this
optical device work and therefore hopefully really push research hard on
resolving some of its problems. I suspect its initial use will be limited to
specialized problems, however.

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fpgaminer
Bosons have a wonderful advantage over fermions. Whereas electrons cannot
occupy the same space at the same time, photons will happily overlap. So,
speaking in broad strokes here, optical computers can certainly have a higher
computational/informational density. However, Optalysys's marketing is
disingenuous when they use the phrases like "computing at the speed of light."
Present day electron based CPUs already compute at the speed of light!

In other words, an optical computer cannot move data from one point to another
any faster than a traditional computer. The latency is the same no matter what
you're computing with.

However, the ability of optical computers to have a higher computing density
(computations per area of space) may negate that issue. Whatever the optical
equivalent of RAM would be, it can be theoretically smaller, and thus help to
relieve some of the latency issue.

Also interesting about optical computers is that they can perform convolutions
for "free". Present day computers are abysmal at convolutions. This is helpful
to image processing, graphics rendering, and neural networks.

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mschuster91
> Present day electron based CPUs already compute at the speed of light!

No, speed is still below _c_ , which is why on high-frequency signal routes on
PCBs the traces must be length-matched, sometimes down to tenths of
millimeters.

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sparky
Propagation velocity in copper is within a factor of 2 or so of c; you would
have to length-match even at vp=c, given a short enough clock period.

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dm2
The title of this article is: "By 2020, you could have an exascale speed-of-
light optical computer on your desk"

We might be able to rent one and have access to it remotely. Right now it's
still in the theory phase, I'm not sure the author of this article realizes
that 2020 is less than 6 years away.

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greyskull
I'm completely clueless about anything relevant to this topic, but that video
blew my mind. Human achievements are incredible.

