diff --git a/2019/ruby/day_07.rb b/2019/ruby/day_07.rb
index df56b57..2773a35 100644
--- a/2019/ruby/day_07.rb
+++ b/2019/ruby/day_07.rb
@@ -2,11 +2,26 @@ require_relative "computer"
 
 program = ARGF.read
 
-puts (0..4).to_a.permutation.map {|phase_settings|
+p (5..9).to_a.permutation.map {|phase_settings|
   amplifiers = Array.new(5) { Computer.from(program) }
-  amplifiers.zip(phase_settings).inject(?0) {|i, (a, ps)|
-    output = StringIO.new
-    a.run(StringIO.new("#{ps}\n#{i}"), output)
-    output.string
-  }.to_i
+
+  pipes = Array.new(5) { IO.pipe }
+
+  # input phase settings
+  pipes.zip(phase_settings).each do |(_, w), ps|
+    w.puts(ps)
+  end
+
+  # first 0 signal
+  pipes.first.last.puts(?0)
+
+  ios = pipes.cycle.each_cons(2).take(5).map {|(r, _), (_, w)| [r, w] }
+
+  ts = amplifiers.zip(ios).map {|(a, (i, o))|
+    Thread.new { a.run(i, o) }
+  }
+  ts.each(&:join)
+
+  thrusters_input = ios.first.first
+  thrusters_input.gets.to_i
 }.max