String reverse benchmarks

string-reverse-benchmark.rb

[179] pry(main)> n = 1000000
=> 1000000
[180] pry(main)> Benchmark.bm(7) do |x|
[180] pry(main)*   x.report('1:') { ->(str) { n.times { chars = str.chars; (1..chars.length).to_a.tap { |a| chars.each_with_index { |c, i| a[-i-1] = c } }.join } }.call('r4v3n') }
[180] pry(main)*   x.report('2:') { ->(str) { n.times { [].tap { |a| chars = str.chars; str.size.times { a << chars.pop } }.join } }.call('r4v3n') }
[180] pry(main)*   x.report('3:') { ->(str) { n.times { str.size/2.times { |i| str[i], str[-i-1] = str[-i-1], str[i] }; str } }.call('r4v3n') }
[180] pry(main)*   x.report('4:') { ->(str) { n.times { str.reverse } }.call('r4v3n') }
[180] pry(main)* end
              user     system      total        real
1:        2.626973   0.019897   2.646870 (  2.657133)
2:        1.911454   0.017483   1.928937 (  1.936380)
3:        1.044563   0.006635   1.051198 (  1.055289)
4:        0.094309   0.000483   0.094792 (  0.095374)
=> [#<Benchmark::Tms:0x00007fdea3db3218 @cstime=0.0, @cutime=0.0, @label="1:", @real=2.657132999971509, @stime=0.01989699999999983, @total=2.6468699999999994, @utime=2.6269729999999996>,
 #<Benchmark::Tms:0x00007fdebaacb7c8 @cstime=0.0, @cutime=0.0, @label="2:", @real=1.9363799998536706, @stime=0.017482999999999915, @total=1.9289370000000026, @utime=1.9114540000000027>,
 #<Benchmark::Tms:0x00007fde9df72eb0 @cstime=0.0, @cutime=0.0, @label="3:", @real=1.0552890002727509, @stime=0.0066349999999997245, @total=1.0511979999999999, @utime=1.0445630000000001>,
 #<Benchmark::Tms:0x00007fdea3fea3d8 @cstime=0.0, @cutime=0.0, @label="4:", @real=0.09537400025874376, @stime=0.0004830000000000112, @total=0.0947919999999991, @utime=0.09430899999999909>]

String#reverse is clear winner.. it is implemented in C in the ruby source -> https://apidock.com/ruby/String/reverse