Refactored solvers with fluent pattern

[nakosung]

I refactored solvers with fluent pattern to add a solver like rmsprop, which isn't included in this PR. After merging this PR, rmsprop will be proposed.

A cool thing introduced by this PR is keeping code DRY(Do not Repeat Yourself). You don't have to write similar code paths for cpu/gpu.

Modified ADAGRAD solver is like below:

op
      // compute square of gradient in update
      .sqr(param, update)
      // update history
      .add(update,history,history)
      // prepare update
      .sqrt(history,update)
      .add_scalar(delta,update)
      .div(param,update,update)      
      // scale and copy
      .axpby(local_rate,update,Dtype(0),param)

[nakosung]

Some tests are failed due to 'different trained weights'. It may not be an 'failure' because I've changed pow into sqr/sqrt, which can drive weights different. If maintainers decide to merge this PR, I'll update test cases.

[jeffdonahue]

This is a cool concept, but I'm not sure we want to adopt a new pattern to unify the math interface specifically for the solvers, as opposed to a more general unification at the level of the math interface itself, as in the device abstraction effort (#610, which should be restored eventually...). Maybe there are some interesting ideas here that could complement that effort though?

[jeffdonahue]

(Sorry, didn't mean to immediately close...)

[shelhamer]

Agreed that this is a neat concept, but it's perhaps too local when done only for the solver.

Re: RMSprop, it is a solver that is on our TODO list so we'd welcome a PR for it.

[sguada]

It would be better if it were part of Blob so it could be used in the
layers.

Sergio

2015-01-21 19:07 GMT-08:00 Evan Shelhamer notifications@github.com:

Agreed that this is a neat concept, but it's perhaps too local when done
only for the solver.

Re: RMSprop, it is a solver that is on our TODO list so we'd welcome a PR
for it.

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#1759 (comment).

[nakosung]

In fact I had implemented RMSprop in this pattern(fluent), PR for RMSprop should be re-written in the orginal caffe style.

[nakosung]

Applying this pattern to whole program will not be a hard thing.

[shelhamer]

@nakosung please PR RMSprop in the current Caffe style first. Once that is in, we can figure out a plan for the fluent style in Caffe. Thanks for both the consideration of how to make the Caffe code more readable and concise.

[nakosung]

@shelhamer Okay, I'll try to PR RMSprop in a separate branch, but for now it doesn't have a priority.