Graph subnetwork: Multiple outputs

[mreppen]

Hi, I finally got around to adding this small change. This was discussed in #491 I personally don't need it, but for the sake of completeness, here it is.

Example:

let nn = Graph.(
  let inp = input [| 2 |] in
  let x1 = lambda ~name:"x1" ~out_shape:[|1|] (fun x -> Algodiff.Maths.get_slice [[]; [0]] x) inp in
  let x2 = lambda ~name:"x2" ~out_shape:[|1|] (fun x -> Algodiff.Maths.get_slice [[]; [1]] x) inp in
  let f1 = fully_connected ~name:"f1" 1 x1 in
  let f2 = fully_connected ~name:"f2" 1 x2 in
  let sum = add ~name:"sum" [| f1; f2 |] in
  sum |> get_network);;
Graph.get_subnetwork ~make_inputs:[|"x1"; "x2"|] nn [| "f1"; "f2" |];;

Two comments:

• I also added a flag for whether to copy the weights.
• I did change the signature (likely not many are using this yet, so hopefully not a problem). This also allowed me to change the default copy behavior to true. If this is undesirable, d684020 is a version without and I can PR that instead.

PS. I have myself found this subnetwork feature really useful :)

[mseri]

I have a minor comment, based on personal preference, otherwise it looks good to me. Please wait some other review before making any change.

[mseri]

I think it would be useful to name the options here:

``get_subnetwork ?copy ?make_inputs network output_names`` constructs a subnetwork of nodes of ``network`` ...

[mreppen]

@mseri's comment makes sense to me as well. I have a commit ready to push.

Another point I forgot to bring up: Would it perhaps make sense to drop or rename the get_-part of the function name? After all, it is not a getter function. Either plain subnetwork or something like make_subnetwork?

[mseri]

Sounds reasonable to me to rename it, this could allow to keep backward compatibility although I don't see the need for this. I think we should wait to see what @jzstark @ryanrhymes or @tachukao think about it.

[tachukao]

agree with the name change, looks good to me!

[ryanrhymes]

Looks very good to me. Both make_subnetwork and subnetwork are fine by me.

[mreppen]

@ryanrhymes, I picked make_subnetwork. @mseri's doc comment is also in the latest commit.