MRI vs JRuby vs JRuby+Java

bench.rb

require 'benchmark'
require 'set'

range = (1..10_000)

subs = {}
clients = (1..5_000).to_a
chosen = clients.sample 50

# NOTE: Hash was added *after* I wrote the OP on Reddit.
puts "#{RUBY_ENGINE} #{RUBY_VERSION} #{RUBY_PLATFORM}"
[ Array, SortedSet, Hash ].each do |klass|
  clients_per = 500 # 10%

  if klass == Hash
    10_000.times{|i| subs["foo:#{i}"] = clients.sample(clients_per).map{|a| [ a, nil ]}.to_h}
  else
    10_000.times{|i| subs["foo:#{i}"] = klass.new clients.sample(clients_per)}
  end

  r = Benchmark.measure do
    subs.each do |_, cur|
      chosen.each{|c| cur.delete c}
    end
  end

  puts klass.name, r
end

java_bench.rb

require 'benchmark'

$CLASSPATH << 'java'
java_import 'foo.SubscriptionManager'

subs = SubscriptionManager.new

clients = (1..5_000).to_a
chosen = clients.sample 50

puts "#{RUBY_ENGINE} #{RUBY_VERSION} #{RUBY_PLATFORM}"
clients_per = 500 # 10%
10_000.times{|i| clients.sample(clients_per).each{|c| subs.add_subscription "foo:#{i}", c} }

r = Benchmark.measure do
  chosen.each{|c| subs.remove_subscriptions_for_user c}
end

puts r

SubscriptionManager.java

// After cloning/copying, run the following commands from the project directory to set it up:
// $ mkdir -p java/foo
// $ mv SubscriptionManager.java java/foo
// $ cd java/foo
// $ javac SubscriptionManager.java
// $ cd ../..
// You can now run the benchmarks yourself.

package foo;

import java.util.HashMap;
import java.util.Map;
import java.util.TreeSet;
import java.util.SortedSet;

class SubscriptionManager {
  private Map<String, SortedSet<Integer>> subscriptions;

  public SubscriptionManager() {
    this.subscriptions = new HashMap<String, SortedSet<Integer>>();
  }

  public SortedSet<Integer> addOrGet(String name) {
    SortedSet<Integer> set = this.subscriptions.get(name);
    if (set == null) {
      set = new TreeSet<Integer>();
      this.subscriptions.put(name, set);
    }

    return set;
  }

  public void addSubscription(String name, Integer user) {
    addOrGet(name).add(user);
  }

  public void removeSubscriptionsForUser(Integer user) {
    for (Map.Entry<String, SortedSet<Integer>> entry : this.subscriptions.entrySet()) {
      entry.getValue().remove(user);
    }
  }

  public Map<String, SortedSet<Integer>> subscriptions() {
    return this.subscriptions;
  }
}