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Facebook Trains ImageNet in 1 Hour

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Re: Facebook Trains ImageNet in 1 Hour

#31

A practically interesting paper. Some insights: 1.Larger batches requires large learning rate. And this paper shows that learning rate can even scale linearly with the batch size, which leading to extremely large learning rate/batch sizes. 2.Larger batch causes initial learning difficult, so this paper proposes to have a warm-up period where during the initial epochs, the learning rate grows from a smaller value grad…

10 node GPU clusters are relatively common at eg Universities.

Re: Facebook Trains ImageNet in 1 Hour

#32

tl;dr they found a clever way to spread the training across 256 GPUs by synchronising the stochastic gradient descent

this seems like the trivial, most obvious way to parallelize training across GPUs. Not, imo, clever. The important bit here is that they've shown that large mini batch sizes still can maintain accuracy if you slow the learning rate.

Lots of clever things are simply self-evident in hindsight.

Re: Facebook Trains ImageNet in 1 Hour

#33
post #27

Looks like Nvidia is doing a proper content marketing push to compete against AMD.

Interestingly enough I think the people who gain the most from this paper are cloud providers. Very few orgs will buy 256 GPUs, but with linear scaling, renting them makes a lot of sense.

There are "only" 32 GPUs in the cluster, with 8 workers per GPU.

Re: Facebook Trains ImageNet in 1 Hour

#35

tl;dr they found a clever way to spread the training across 256 GPUs by synchronising the stochastic gradient descent

this seems like the trivial, most obvious way to parallelize training across GPUs. Not, imo, clever. The important bit here is that they've shown that large mini batch sizes still can maintain accuracy if you slow the learning rate.

Just because it's simple to explain at a high level doesn't make it trivial.

Plenty of theoretically trivial solutions to problems are absolute pains to implement. I mean there are entire companies that at their core solve relatively "trivial" problems but employ huge numbers of engineers. Just because the core concept is simple to explain doesn't mean it's easy.

Re: Facebook Trains ImageNet in 1 Hour

#36
post #31

A practically interesting paper. Some insights: 1.Larger batches requires large learning rate. And this paper shows that learning rate can even scale linearly with the batch size, which leading to extremely large learning rate/batch sizes. 2.Larger batch causes initial learning difficult, so this paper proposes to have a warm-up period where during the initial epochs, the learning rate grows from a smaller value grad…

10 node GPU clusters are relatively common at eg Universities.

Concur. I threw 2x GTX 980s in one of our testbeds two years ago just to make it more generally useful, giving us a 20 GPU cluster. Next time we do it, I'll aim for 4x1080ti or the equivalent. It's painful to power and cool those in lower-end university machine rooms, but it's possible. 10x 4x1080ti machines is only about 15kW, which is high but not insane. It's also only about $60k USD. Also something that a pool of faculty can afford.

I've been experimenting with really low-end builds for that design recently. https://goo.gl/photos/6bDLjJqGAwhG7hGP9

That's a consumer/gaming motherboard (asrock supercarrier), which doesn't have enough PCIe bandwidth to support the cards, but part of what we're researching are ways to reduce synchronization bandwidth. I wouldn't recommend that route as a general approach, though - not flexible enough for future uses. The 8x 1080ti Supermicro build posted a few days ago is probably a better choice: https://news.ycombinator.com/item?id=14508928

The problem is that one student can easily tie up the entire cluster for half the duration of her Ph.D. Machine learning people have voracious appetites for compute. :)

Re: Facebook Trains ImageNet in 1 Hour

#37

A practically interesting paper. Some insights: 1.Larger batches requires large learning rate. And this paper shows that learning rate can even scale linearly with the batch size, which leading to extremely large learning rate/batch sizes. 2.Larger batch causes initial learning difficult, so this paper proposes to have a warm-up period where during the initial epochs, the learning rate grows from a smaller value grad…

I disagree that this is not an architecture for others. We are a research lab, and we're building a distributed cluster. Cheap infiniband. Lots of gtx1080Tis. It's not that expensive to have a 40-GPU cluster with 10 4U servers (about 100K Euro).

Are you going to rent access to your cluster? :)

Re: Facebook Trains ImageNet in 1 Hour

#38
post #33
post #27

Earlier quoted context omitted.

Interestingly enough I think the people who gain the most from this paper are cloud providers. Very few orgs will buy 256 GPUs, but with linear scaling, renting them makes a lot of sense.

There are "only" 32 GPUs in the cluster, with 8 workers per GPU.

They had 32 servers in the cluster, each with 8 P100 GPUs. Each GPU was one "worker" in their parlance.

("How to train ResNet-50 in one hour on two million dollars of hardware." :-)

Re: Facebook Trains ImageNet in 1 Hour

#39

Earlier quoted context omitted.

I disagree that this is not an architecture for others. We are a research lab, and we're building a distributed cluster. Cheap infiniband. Lots of gtx1080Tis. It's not that expensive to have a 40-GPU cluster with 10 4U servers (about 100K Euro).

What mobo/CPU are you using? How much RAM in each server? Can you provide some more detailed specs? Thanks!

CPU is not that important. A motherboard that has PCIe 3.0 and 7 PCIx16 slots is ok for at least 3 GPUs. Each GPU takes typically two slots. Then, a >1400 Watts PSU. Here is a relatively cheap box that also has 8 disk slots (for hadoop): https://exxactcorp.com/index.php/solution/solu_detail/320

Re: Facebook Trains ImageNet in 1 Hour

#40
post #37

Earlier quoted context omitted.

I disagree that this is not an architecture for others. We are a research lab, and we're building a distributed cluster. Cheap infiniband. Lots of gtx1080Tis. It's not that expensive to have a 40-GPU cluster with 10 4U servers (about 100K Euro).

Are you going to rent access to your cluster? :)

To users in Sweden at www.hops.site It provides Jupyter/Hadoop/Spark/Tensorflow and GPUs (as a resource in YARN).
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