I tried to be able to pass multiple objects with Ractor

Conclusion

I tried to make the following code work with Ractor.

r = Ractor.new do
    v1, v2 = Ractor.recv
    puts v1
    puts v2
    puts v1.class
    puts v2.class
end

r.send(1, 2)

r.take
# => 1
# => 2
# => Integer
# => Integer

What is Ractor?

It is a mechanism to provide parallel / parallel functions introduced in Ruby3. Originally named Guild, it has been discussed for several years.

For more details, please refer to the video below.

[JA] Ractor report / Koichi Sasada @ko1

Pass the object to Ractor

You can pass an object to Ractor using the send method.

r = Ractor.new do
    v = Ractor.recv
    puts v
    puts v.class
end

r.send(1)

r.take
# => 1
# => Integer

However, you cannot pass multiple objects as shown below.

r = Ractor.new do
    v1, v2 = Ractor.recv
    puts v1
    puts v2
    puts v1.class
    puts v2.class
end

r.send(1, 2)

r.take
# =>wrong number of arguments (given 2, expected 1) (ArgumentError)

However, it seems OK to pass it as an array.

r = Ractor.new do
    v1, v2 = Ractor.recv
    puts v1
    puts v2
    puts v1.class
    puts v2.class
end

r.send([1, 2])

r.take
# => 1
# => 2
# => Integer
# => Integer

Looking at the implementation, it looks like this (in ractor.rb in the CRuby source code) The current send method takes only one object as an argument. You can also specify whether or not to move with the keyword argument move.

  def send obj, move: false
    __builtin_cexpr! %q{
      ractor_send(ec, RACTOR_PTR(self), obj, move)
    }
  end

The C function is called with __builtin_cexpr!, and the argument received by the method is passed to the C function as it is. As an aside, recent CRuby allows you to write code that passes Ruby variables to C functions as an internal implementation.

What i did

I rewrote Ractor's send method as follows.

  def send obj, *arg, move: false
    obj = arg.unshift obj unless arg.empty?
    __builtin_cexpr! %q{
      ractor_send(ec, RACTOR_PTR(self), obj, move)
    }
  end

First, the send method always takes one object as an argument. The arguments are rewritten like ʻobj, * arg, move: falseto maintain that behavior. Also, if multiple objects are passed, such assend (1, 2), the arguments are passed as an array to * arg`.

If ʻarg is not an empty array, then multiple objects are being passed, and the ʻobj that is finally passed to the C function is converted to a merge of the first argument and the variadic argument. I will.

All you have to do is build the modified CRuby source code.

You can now pass multiple objects to Ractor as follows:

r = Ractor.new do
    v1, v2 = Ractor.recv
    puts v1
    puts v2
    puts v1.class
    puts v2.class
end

r.send(1, 2)

r.take
# => 1
# => 2
# => Integer
# => Integer

reference

ref: Guild → Ractor ref: https://github.com/ko1/ruby/blob/ractor/ractor.ja.md ref: [[JA Ractor report / Koichi Sasada @ko1

Postscript

By the way, if you want a monkey patch, you can create a method wrapped as follows.

class Ractor
    def multi_send(obj, *args, move: true)
        obj = args.unshift obj unless args.empty?
        send(obj, move: move)
    end 
end

r = Ractor.new do
    v1, v2 = Ractor.recv
    puts v1
    puts v2
    puts v1.class
    puts v2.class
end

r.multi_send(1, 2)

r.take

The range of monkey patches is wide, so if you use them in practice, it may be better to use refinements because it has less effect.

module RefineRactor
    refine Ractor do
        def multi_send(obj, *args, move: true)
            obj = args.unshift obj unless args.empty?
            send(obj, move: move)
        end 
    end
end

using RefineRactor

r = Ractor.new do
    v1, v2 = Ractor.recv
    puts v1
    puts v2
    puts v1.class
    puts v2.class
end

r.multi_send(1, 2)

r.take