Fix named_modules

[nerdinand]

Fix undefined method `include?' for nil:NilClass in Torch::NN::Module#named_modules

[ankane]

Hey @nerdinand, thanks for the PR! Can you paste the stack trace of the error you're seeing? memo is set two lines below the change, so I'm not sure this will fix the error.

[nerdinand]

Without this I'm getting:

	3: from /Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/torch-rb-0.3.0/lib/torch/nn/module.rb:119:in `load_state_dict'
	2: from /Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/torch-rb-0.3.0/lib/torch/nn/module.rb:119:in `each'
	1: from /Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/torch-rb-0.3.0/lib/torch/nn/module.rb:121:in `block in load_state_dict'
/Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/torch-rb-0.3.0/lib/torch/nn/module.rb:192:in `named_modules': undefined method `include?' for nil:NilClass (NoMethodError)

[ankane]

Is there a chance you removed the memo ||= Set.new in your local installation? The include? check should be on line 193 instead of 192. If that's not the issue, can you share a minimal script to reproduce?

[nerdinand]

For some reason, when installing torch.rb with

gem 'torch-rb', github: 'ankane/torch.rb'

then i get

/Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:92:in `require': cannot load such file -- torch (LoadError)

when i require 'torch'.

It also gives me these warnings while bundling, not sure if that means anything:

Using torch-rb 0.3.0 from https://github.com/ankane/torch.rb.git (at master@f2f4cba)
/Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/2.7.0/rubygems/ext/builder.rb:165: warning: conflicting chdir during another chdir block
/Users/ferdi/.rbenv/versions/2.7.1/lib/ruby/2.7.0/rubygems/ext/builder.rb:173: warning: conflicting chdir during another chdir block

But yes, I guess you're right, I must have changed it locally. When installing 0.3.0 from rubygems it looks like this:

      # TODO return enumerator?
      def named_modules(memo: nil, prefix: "")
        ret = {}
        memo ||= Set.new
        unless memo.include?(self)
          memo << self
          ret[prefix] = self
          named_children.each do |name, mod|
            next unless mod.is_a?(Module)
            submodule_prefix = prefix + (!prefix.empty? ? "." : "") + name
            mod.named_modules(memo: memo, prefix: submodule_prefix).each do |m|
              ret[m[0]] = m[1]
            end
          end
        end
        ret
      end

(of course with the bug from #9 again)

[ankane]

I'm not able to reproduce the require "torch" error when installing from GitHub unfortunately. Make sure your Ruby script is configured to use Bundler.

require "bundler/setup"
require "torch"

The Bundler warnings aren't anything to worry about (not specific to Torch.rb).

[nerdinand]

Hmm, very interesting, that indeed in this case i need

require 'bundler/setup'

for it to work... Or indeed running with bundle exec also does the trick...

[ankane]

Glad that fixed it. The reason is Ruby doesn't know how to find gems installed by Bundler from GitHub without Bundler (if that makes any sense).