benchmark_maps.rb

require 'benchmark'

hash  = { a: 'a', b: 'b', c: 'c', d: 'd' }.freeze
keys  = [:a, :b].freeze

n = 500_000

Benchmark.bm do |x|
  x.report do
    n.times do
      hash1 = hash.dup
      hash1.delete_if {|key, _| keys.include?(key)}
    end
  end

  x.report do
    n.times do
      hash2 = hash.dup
      keys.each do |key|
        hash2.delete(key)
      end
    end
  end
end