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Google supercharges machine learning tasks with TPU custom chip

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Re: Google supercharges machine learning tasks with TPU custom chip

#91
post #75
post #12

Earlier quoted context omitted.

From the article: "TPU is tailored to machine learning applications, allowing the chip to be more tolerant of reduced computational precision, which means it requires fewer transistors per operation."

Do you reckon that means it's using small floats?

Or small ints, possibly working in log space.

Re: Google supercharges machine learning tasks with TPU custom chip

#92
post #62
post #43

Earlier quoted context omitted.

I would be shocked if tensorflow optimizations where useful 1:1 for stock Intel chips or GPU's. So, there is still plenty of lock-in even if your process runs. GPU vendors love to play this game by helping optimize games.

It's possible, but I think that the majority of ML optimization as seen by a programmer using tensorflow is more about optimizing the balance of accuracy, training & inference speed, and memory use, and a lot of the solutions in this space are pretty hardware independent. There's an entire other type of optimization about, e.g., making conv2d insanely fast, but that's not something that a typical data scientist-type…

I am more thinking in terms of:

  1. Best price/performance is tensorflow right now. So, the best software choice is platform X.  
  2. Then in 2 years.. Well we are using Platform X so tensorflow is clearly the best option.
In other words once you pick conv2d, you tend to also stick with whatever conv2d is optimized for. Which also means HW vendors love to help optimize popular platforms.

Re: Google supercharges machine learning tasks with TPU custom chip

#93

3 generations ahead of moore law??? I really wonder how they are accomplishing this beyond implementing the kernels in hardware. I suspect they are using specialized memory and an extremely wide architecture. Sounds they also used this for AlphaGo. I wonder how badly we were off on AlphaGo's power estimates. Seems everyone assumed they were using GPU's, sounds like they were not. At least partially. I would really LO…

But isn't 3 generations ahead just 8x? Which doesn't sound at all unreasonable for a custom hardware.

The rule of thumb I was taught was that going from a DSP/GPU to a custom ASIC would give you a 10X advantage in performance/power which is pretty close to this. And look at how much bitcoin mining ASICs out compete GPUs.

Re: Google supercharges machine learning tasks with TPU custom chip

#94
post #72

Earlier quoted context omitted.

> By revealing that AlphaGo was based on this hardware Interesting, as the nature/science paper made no mention of this, it was exclusively trained on GPUs.

Training and inference are not the same thing.

Sure... I think you are missing the point. In Nov., the Nature paper which contains the AlphaGo algorithm, the hardware detailed was exclusively CPU+GPUs.

Between that time and the Lee Sedol match, the hardware running AlphaGo was switched, to these TPU.

From the paper: "The final version of AlphaGo used 40 search threads, 48 CPUs, and 8 GPUs. We also implemented a distributed version of AlphaGo that exploited multiple machines, 40 search threads, 1,202 CPUs and 176 GPUs."

Re: Google supercharges machine learning tasks with TPU custom chip

#95

This is huge. If they really do offer such a perf/watt advantage, they're serious trouble for NVIDIA. Google is one of only a handful of companies with the upfront cash to make a move like this. I hope we can at least see some white papers soon about the architecture--I wonder how programmable it is.

There's no way Google lets this leave their datacenters. Chip fabrication is a race to the bottom at this point. [1] Google is doubling down on hosting as a source of future revenue, and they're doing that by building an ecosystem around Tensorflow. What I think is interesting is how weak Apple looks. Amazon has the talent and money to be able to compete with Google on this playing field. Microsoft is late, but they…

> There's no way Google lets this leave their datacenters. Chip fabrication is a race to the bottom at this point. [1]

I’d hope someone somewhere steals the blueprints and posts all of them publicly online.

The whole point of patents was that companies would publish everything, but get 20 years of protection.

But by now, especially companies like Google don’t do so anymore – and everyone loses out.

EDIT: I’ll add the standard disclaimer: If you downvote, please comment why – so an actual discussion can appear, which usually is a lot more useful to everyone.

Re: Google supercharges machine learning tasks with TPU custom chip

#96
post #63

I'm happy to hear that this is finally public so I can actually talk about the work I did when I was at Google :-). I'm a bit surprised they announced this, though. When I was there, there was this pervasive attitude that if "we" had some kind of advantage over the outside world, we shouldn't talk about it lest other people get the same idea. To be clear, I think that's pretty bad for the world and I really wished th…

Wouldn't you typically prototype the design on an FPGA and then manufacture an ASIC once you'd worked out the kinks?

Re: Google supercharges machine learning tasks with TPU custom chip

#97
There is not a single number in this article.

Now these heatsinks can be deceiving for boards that are meant to be in a server rack unit with massive fans throwing a hurricane over them, but even then that is not very much power we're looking at there.

Re: Google supercharges machine learning tasks with TPU custom chip

#98

I'm guessing that the performance / watt claims are heavily predicated on relatively low throughput, kind of similar to ARM vs Intel CPUs - particularly because they're only powering it & supplying bandwidth via what looks like a 1X PCIE slot. IOW, taking their claims at face value, a Nvidia card or Xeon Phi would be expected to smoke one of these, although you might be able to run N of these in the same power envelo…

> I'm guessing that the performance / watt claims are heavily predicated on relatively low throughput, kind of similar to ARM vs Intel CPUs - particularly because they're only powering it & supplying bandwidth via what looks like a 1X PCIE slot.

Agreed. Also tells you that they don't need to communicate with the CPU much, given that it only has a PCIE. Reminds me of Knights Ferry, in this respect.

> a Nvidia card or Xeon Phi would be expected to smoke one of these

Will be very interesting to see some head-to-head benchmarks between these guys (on tensorflow and other libraries) in the next few months. Especially as Knights Landing starts to appear, and the new Nvidia card.

Re: Google supercharges machine learning tasks with TPU custom chip

#99
post #58

I wouldn't be surprised if Google is looking to build (or done so already) a highly dense and parallel analog computer with limited precision ADC/DACs. I mean that's simplifying things quite a bit, but it would probably map pretty well to the Tensorflow application.

What are the advantages of analog computing for this application?

If you have an application that can tolerate error (like classification), then analog computing can give enormous gains in terms of speed _and_ power efficiency. Essentially, the savings come from using physics to perform the math (see Kirchhoff's current law) vs. using discrete time steps vs. fully-unrolling the logic. Google may not be using analog processing for this version, but I read an analog neural network researcher's page who said he moved to Google last year. (Sorry, I can't find the page again, but I think he was from the UK.)

Re: Google supercharges machine learning tasks with TPU custom chip

#100

Earlier quoted context omitted.

"Backprop" isn't even close to something that would be a "CPU instruction", it's an entire class of algorithm. It's like saying "calculus" should be a CPU instruction. Matrix multiplication & other operations, on the other hand, do neatly decompose into such instructions, which have been implemented by NVidia et al., since that's the core set of functionality they've been pushing for like a decade now. Additional die…

That was my impression too. ML under the hood was a lot of linear algebra, not very different than most shaders. But maybe Google decided to hardcode a few important ML primitives because the ROI was that good in terms of grabbing customers. Also they might have very large scale applications not found elsewhere that motivates this.

Ok I was obviously oversimplifying things but my point is since we can only speculate, it's clear that when you know specific algorithms/math operations/memory layouts/applications you want to optimize for you can create dedicated chips that optimize and do that quickly. That bitcoin miners are all dedicated chips and run circles around GPUs demonstrates exactly this fact.

Furthermore the fact that ML can be error tolerant means you also get to optimize certain floating point operations for speed or energy efficiency at the cost of accuracy. NVIDIA doesn't get to do this in their linear algebra support.

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