example.rb

require 'tensorflow'
graph = Tensorflow::Graph.new
tensor_1 = Tensorflow::Tensor.new([[2, 2.3], [ 10, 6.2]])
tensor_2 = Tensorflow::Tensor.new([[4, 3.2], [ 47, 1.2]])
placeholder_1 = graph.placeholder('tensor1', tensor_1.type_num)
placeholder_2 = graph.placeholder('tensor2', tensor_2.type_num)
opspec = Tensorflow::OpSpec.new('Addition_of_tensors', 'Add', nil, [placeholder_1, placeholder_2])

op = graph.AddOperation(opspec)
session_op = Tensorflow::Session_options.new
session = Tensorflow::Session.new(graph, session_op)
hash = {}
hash[placeholder_1] = tensor_1
hash[placeholder_2] = tensor_2
result = session.run(hash, [op.output(0)], [])
print result[0], "\n"

Just a set of small "more ruby-ish" code changes for this example:

graph = Graph.new
input1 = graph.placeholder(:input1, Tensorflow::TF_DOUBLE, [2,3])
input2 = graph.placeholder(:input2, Tensorflow::TF_DOUBLE, [2,3])
graph.op_definer(:Add,:output, [input1, input2], "", nil) # or maybe even :add, I'm not sure if it is internal TensorFlow op
encoder = Tensorflow::GraphDef.encode(graph.graph_def)
session = Session.new
graph.graph_def_raw = encoder
session.extend_graph(graph)
input1 = Tensor.new([[1.0,3.0, 5.0],[2.0,4.0, 7.0]])
input2 = Tensor.new([[-5.0,1.2,4.5],[8.0,2.3, 3.1]])
input = {
  input1: input1.tensor,
  input2: input2.tensor
}
result = session.run(input, [:output], nil)
puts result.first

Also, note that sometimes you use namespace (Tensorflow::GraphDef), and sometimes not (Session.new). Also, I suppose TensorFlow is more correct as a namespace name.

(It is pretty small "first glance" changes, just for the showcase sake)

Yeah, definitely not the empty () parenthesis if not parameters.

Regarding using symbols instead of strings, we need to be careful initially, because TensorFlow complains if we pass it a Symbol as the key. So at some point we should convert any placeholder names/keys to String before passing them on to TensorFlow and maybe use HashWithIndifferentAccess when a tensor is fetched from TensorFlow.