Adadelta

[mohomran]

Initial implementation of the Adadelta solver as proposed in "ADADELTA: An Adaptive Learning Rate Method" (Zeiler, 2012). Motivation: http://cs.stanford.edu/people/karpathy/convnetjs/demo/trainers.html

Performance on the MNIST autoencoder demo is more or less on par with standard SGD+momentum but not as good as the Nesterov solver. The lack of a learning rate does seem to be a problem towards later iterations in that loss/accuracy don't entirely converge, but this could be due to an implementation issue.

Iteration 64500, Testing net (#0)
Test loss: 59.4627
    Test net output #0: cross_entropy_loss = 59.4627 (* 1 = 59.4627 loss)
    Test net output #1: l2_error = 1.82881
Iteration 64500, Testing net (#1)
Test loss: 59.7422
    Test net output #0: cross_entropy_loss = 59.7422 (* 1 = 59.7422 loss)
    Test net output #1: l2_error = 1.92399
Iteration 65000, loss = 62.1569
Iteration 65000, Testing net (#0)
Test loss: 60.7756
    Test net output #0: cross_entropy_loss = 60.7756 (* 1 = 60.7756 loss)
    Test net output #1: l2_error = 2.05861
Iteration 65000, Testing net (#1)
Test loss: 61.0705
    Test net output #0: cross_entropy_loss = 61.0705 (* 1 = 61.0705 loss)
     Test net output #1: l2_error = 2.15354

(for comparison see: #741 (comment))

A couple of things to note:

• Adadelta requires the tracking of both gradient and update history. I chose to store both sequentially in "history_" for a couple of reasons, e.g. to reuse SnapshotSolverState() and RestoreSolverState().
• All the tests pass, but a couple (those with multiple iterations) are ridiculously slow, even though the MNIST demo for example is not noticeably slower with Adadelta compared to the other solvers. I still need to look into this.

[shelhamer]

Good start! Comment once you've investigated the initial issues for review.

On Saturday, September 20, 2014, Mohamed Omran notifications@github.com
wrote:

Initial implementation of the Adadelta solver as proposed in "ADADELTA: An
Adaptive Learning Rate Method" (Zeiler, 2012). Motivation:
http://cs.stanford.edu/people/karpathy/convnetjs/demo/trainers.html

Performance on the MNIST autoencoder demo is more or less on par with
standard SGD+momentum but not as good as the Nesterov solver. The lack of a
learning rate does seem to be a problem towards later iterations in that
loss/accuracy don't entirely converge, but this could be due to an
implementation issue.

Iteration 64500, Testing net (#0)
Test loss: 59.4627
Test net output #0: cross_entropy_loss = 59.4627 (* 1 = 59.4627 loss)
Test net output #1: l2_error = 1.82881
Iteration 64500, Testing net (#1)
Test loss: 59.7422
Test net output #0: cross_entropy_loss = 59.7422 (* 1 = 59.7422 loss)
Test net output #1: l2_error = 1.92399
Iteration 65000, loss = 62.1569
Iteration 65000, Testing net (#0)
Test loss: 60.7756
Test net output #0: cross_entropy_loss = 60.7756 (* 1 = 60.7756 loss)
Test net output #1: l2_error = 2.05861
Iteration 65000, Testing net (#1)
Test loss: 61.0705
Test net output #0: cross_entropy_loss = 61.0705 (* 1 = 61.0705 loss)
Test net output #1: l2_error = 2.15354

A couple of things to note:

• Adadelta requires the tracking of both gradient and update history.
  I chose to store both sequentially in "history_" for a couple of reasons,
  e.g. to reuse SnapshotSolverState() and RestoreSolverState.
• All the tests pass, but a couple (those with multiple iterations)
  are ridiculously slow, even though the MNIST demo for example is not
  noticeably slower with Adadelta compared to the other solvers. I still need
  to look into this.

---

You can merge this Pull Request by running

git pull https://github.com/mohomran/caffe adadelta

Or view, comment on, or merge it at:

#1122
Commit Summary

• implemented basic AdaDelta (section 3.1 in paper) + simple test cases
• full adadelta + additional tests
• mnist demos with adadelta

File Changes

• A examples/mnist/lenet_adadelta_solver.prototxt
  https://github.com/BVLC/caffe/pull/1122/files#diff-0 (22)
• A examples/mnist/mnist_autoencoder_solver_adadelta.prototxt
  https://github.com/BVLC/caffe/pull/1122/files#diff-1 (17)
• A examples/mnist/train_mnist_autoencoder_adadelta.sh
  https://github.com/BVLC/caffe/pull/1122/files#diff-2 (4)
• M include/caffe/solver.hpp
  https://github.com/BVLC/caffe/pull/1122/files#diff-3 (23)
• M src/caffe/proto/caffe.proto
  https://github.com/BVLC/caffe/pull/1122/files#diff-4 (1)
• M src/caffe/solver.cpp
  https://github.com/BVLC/caffe/pull/1122/files#diff-5 (199)
• M src/caffe/test/test_gradient_based_solver.cpp
  https://github.com/BVLC/caffe/pull/1122/files#diff-6 (105)

Patch Links:

• https://github.com/BVLC/caffe/pull/1122.patch
• https://github.com/BVLC/caffe/pull/1122.diff

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#1122.

Evan Shelhamer

[muupan]

Hello,

I'm currently using this PR in my project (https://github.com/muupan/dqn-in-the-caffe). I think allowing base_lr and lr_policy will be helpful in case AdaDelta does not coverge. In my case, using original AdaDelta caused divergence, so I multiplied the gradients updates by 0.2 and it worked.

With respect to the slow tests, I wonder why kNumIters for AdaDeltaSolver are very large (=500),

https://github.com/mohomran/caffe/blob/adadelta/src/caffe/test/test_gradient_based_solver.cpp#L566
https://github.com/mohomran/caffe/blob/adadelta/src/caffe/test/test_gradient_based_solver.cpp#L577

while those for other solvers are small (=4).

https://github.com/mohomran/caffe/blob/adadelta/src/caffe/test/test_gradient_based_solver.cpp#L390
https://github.com/mohomran/caffe/blob/adadelta/src/caffe/test/test_gradient_based_solver.cpp#L379

Are these 500 iterations necessary?

[mohomran]

• slow tests: The slowness of the tests seems to have nothing to do with the number of iterations, but rather how I'm storing both update and gradient history. It's unreasonably slow even with for a small number of iterations. I haven't had a chance to look into it in detail
• learning rate: Yes, I suspect that the lack of some global learning rate might be a problem. It could also be that the history needs to be randomly initialised, since the initial step size is otherwise too large and takes a while to decrease to a reasonable value. It could also be a bug. I would need to double check the implementation against the one in ConvNetJS, but I can only get around to it next week.

Thank you for the feedback!

[shelhamer]

Replaced by #2204. Thanks for starting this @mohomran!