update roadmap

[geoffreylitt]

Just some minor tweaks to the Readme and Roadmap, to make it slightly more accessible for new users/contributors. The only really substantive change is adding support for default graphs to the roadmap.

Let me know if you think these changes make sense @Arafatk! Also I would be happy to work on default graph support if you agree that that is worth having. (Technically that's necessary for the basic usage tutorial, and I think it's a pretty important convenience for new users)

[arafatkatze]

@geoffreylitt Thanks for this. It would be really nice to have default graphs. If you wish to work on it, that would be good.

[geoffreylitt]

@Arafatk I'm thinking an interface that's something like this below, making variable available as some sort of global method in addition to just on a graph instance. It would be great to know if you had other thoughts before I get too far implementing.

var1 = Tensorflow::Variable.new([1, 2, 3], dtype: :int32) # assigns to the default graph

The Tensorflow::Variable.new part feels a bit ugly compared to the python tf.variable, another approach might be a singleton object of some kind.

tf = Tensorflow::Coordinator.new  # there is probably a better name for this singleton
var1 = tf.variable([1, 2, 3], dtype: :int32)

Ruby blocks could also easily support assigning a default graph:

graph2 = Tensorflow::Graph.new
graph2.as_default do
  var1 = Tensorflow::Variable.new([1, 2, 3], dtype: :int32) 
end

[arafatkatze]

@geoffreylitt Among the two approaches, I think that having a graph as a global method in addition to having an on graph instance would be the very appropriate and easy to use and obviously it must have support to work easily with placeholder, variable and constant. Thanks for this.

[chrhansen]

@geoffreylitt I also think that would be a great idea to have default graph and eventually also default session. As @Arafatk says, there's a similar behavior in constant and placeholder.

Note how they in the Python api for Variable https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/ops/variables.py#L30, call get_default_graph(), here https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/ops/variables.py#L337, to fetch from here which is then fetched from here: https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/framework/ops.py#L3719.

This and even more so the tf.Session (that automatically assumes the default graph), would also be useful in specs and other places where we constantly have to write 3-4 lines just to evaluate a tensor.

[geoffreylitt]

Thanks for the responses guys. Good point re: also supporting placeholder/constant/etc. I was thinking of a very similar implementation using a thread variable.

I'm not quite clear which of the two proposed interfaces you guys prefer and would love to get a temperature read.

Option A: Use constructors on Tensorflow classes

var1 = Tensorflow::Variable.new([1, 2, 3], dtype: :int32)
placeholder = Tensorflow::Placeholder.new([2, 2])

Option B: Have an object with helper methods defined on it

tf = Tensorflow::Coordinator.new  # there is probably a better name for this singleton
var1 = tf.variable([1, 2, 3], dtype: :int32)
placeholder = tf.placeholder([2, 2])

To me, Option A feels slightly more like what one might expect from standard Ruby, but Option B achieves closer similarity to the feel of the Python library, which seems important. Interestingly, Option B actually isn't that different from just creating a graph instance, so I'm starting to question how useful it would really be.

[chrhansen]

@geoffreylitt I also think Option A would look more familiar to Ruby'ers. If we're consistent in how we translate the python API to Ruby, users should more easy be able to understand the Ruby API. Option A could also be we written with convenience class-methods so we don't have to write .new, and that should make it a bit shorter and bit closer to the Python API. e.g

module CrazyTensorFlowCoordinator
  def self.variable(value, dtype: nil)
    Variable.new(value, dtype: dtype)
  end
end

or whatever you think is the cleanest.