bench_hash_to_proc.rb

require 'benchmark'

hash = { a: 1, b: 2, c: 3 }
keys = %i[a c d]
hash_proc = hash.to_proc

n = 500000

Benchmark.bmbm do |x|
  x.report('&hash') { n.times do
                        keys.map(&hash)
                      end }
  x.report('&hash_proc') { n.times do
                       keys.map(&hash_proc)
                     end }  
  x.report('proc.call(k)') { n.times do
                          keys.map { |k| hash_proc.call(k) }
                        end }  
  x.report('hash[k]') { n.times do
                         keys.map { |k| hash[k] }
                       end }
  x.report('cycle:normal') {
    keys.cycle(1000000).map { |k| hash[k] }
  }
  x.report('cycle:&hash') {
    keys.cycle(1000000).map(&hash)
  }

end

result.txt

Rehearsal ------------------------------------------------
&hash          0.250000   0.010000   0.260000 (  0.266237)
&hash_proc     0.120000   0.000000   0.120000 (  0.122022)
proc.call(k)   0.220000   0.000000   0.220000 (  0.228005)
hash[k]        0.160000   0.000000   0.160000 (  0.168149)
cycle:normal   0.290000   0.020000   0.310000 (  0.312707)
cycle:&hash    0.150000   0.010000   0.160000 (  0.160121)
--------------------------------------- total: 1.230000sec

                   user     system      total        real
&hash          0.260000   0.000000   0.260000 (  0.274470)
&hash_proc     0.110000   0.010000   0.120000 (  0.119108)
proc.call(k)   0.220000   0.000000   0.220000 (  0.230564)
hash[k]        0.150000   0.000000   0.150000 (  0.161705)
cycle:normal   0.300000   0.010000   0.310000 (  0.321791)
cycle:&hash    0.150000   0.000000   0.150000 (  0.165133)