Fast Ruby

In Erik Michaels-Ober's great talk, 'Writing Fast Ruby': Video @ Baruco 2014, Slide, he presented us with many idioms that lead to faster running Ruby code. He inspired me to document these to let more people know. I try to link to real commits so people can see that this can really have benefits in the real world. This does not mean you can always blindly replace one with another. It depends on the context (e.g. gsub versus tr). Friendly reminder: Use with caution!

Each idiom has a corresponding code example that resides in code.

All results listed in README.md are running with Ruby 2.2.0p0 on OS X 10.10.1. Machine information: MacBook Pro (Retina, 15-inch, Mid 2014), 2.5 GHz Intel Core i7, 16 GB 1600 MHz DDR3. Your results may vary, but you get the idea. : )

You can checkout the GitHub Actions build for these benchmark results ran against different Ruby implementations.

Let's write faster code, together! <3

Analyze your code

Checkout the fasterer project - it's a static analysis that checks speed idioms written in this repo.

Measurement Tool

Use benchmark-ips (2.0+).

Template

require "benchmark/ips"

def fast
end

def slow
end

Benchmark.ips do |x|
  x.report("fast code description") { fast }
  x.report("slow code description") { slow }
  x.compare!
end

Idioms

Index

• General
• Array
• Date
• Enumerable
• Hash
• Proc & Block
• String
• Time
• Range

General

attr_accessor vs getter and setter code

https://www.omniref.com/ruby/2.2.0/files/method.h?#annotation=4081781&line=47

$ ruby -v code/general/attr-accessor-vs-getter-and-setter.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]
Calculating -------------------------------------
   getter_and_setter    61.240k i/100ms
       attr_accessor    66.535k i/100ms
-------------------------------------------------
   getter_and_setter      1.660M (± 9.7%) i/s -      8.267M
       attr_accessor      1.865M (± 9.2%) i/s -      9.248M

Comparison:
       attr_accessor:  1865408.4 i/s
   getter_and_setter:  1660021.9 i/s - 1.12x slower

begin...rescue vs respond_to? for Control Flow code

$ ruby -v code/general/begin-rescue-vs-respond-to.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
      begin...rescue    29.452k i/100ms
         respond_to?   106.528k i/100ms
-------------------------------------------------
      begin...rescue    371.591k (± 5.4%) i/s -      1.855M
         respond_to?      3.277M (± 7.5%) i/s -     16.299M

Comparison:
         respond_to?:  3276972.3 i/s
      begin...rescue:   371591.0 i/s - 8.82x slower

define_method vs module_eval for Defining Methods code

$ ruby -v code/general/define_method-vs-module-eval.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
module_eval with string 125.000  i/100ms
       define_method    138.000  i/100ms
-------------------------------------------------
module_eval with string   1.130k (±20.3%) i/s -      5.500k
       define_method      1.346k (±25.9%) i/s -      6.348k

Comparison:
       define_method:        1345.6 i/s
module_eval with string:     1129.7 i/s - 1.19x slower

String#constantize vs a comparison for inflection code

ActiveSupport's String#constantize "resolves the constant reference expression in its receiver".

Read the rationale here

ruby 2.7.3p183 (2021-04-05 revision 6847ee089d) [x86_64-darwin20]

Calculating -------------------------------------
using an if statement
                          8.124M (± 1.8%) i/s -     41.357M in   5.092437s
  String#constantize      2.462M (± 2.4%) i/s -     12.315M in   5.004089s

Comparison:
using an if statement:  8123851.3 i/s
  String#constantize:  2462371.2 i/s - 3.30x  (± 0.00) slower

raise vs E2MM#Raise for raising (and defining) exceptions code

Ruby's Exception2MessageMapper module allows one to define and raise exceptions with predefined messages.

$ ruby -v code/general/raise-vs-e2mmap.rb
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-darwin14]

Calculating -------------------------------------
Ruby exception: E2MM#Raise
                         2.865k i/100ms
Ruby exception: Kernel#raise
                        42.215k i/100ms
-------------------------------------------------
Ruby exception: E2MM#Raise
                         27.270k (± 8.8%) i/s -    137.520k
Ruby exception: Kernel#raise
                        617.446k (± 7.9%) i/s -      3.082M

Comparison:
Ruby exception: Kernel#raise:   617446.2 i/s
Ruby exception: E2MM#Raise:    27269.8 i/s - 22.64x slower

Calculating -------------------------------------
Custom exception: E2MM#Raise
                         2.807k i/100ms
Custom exception: Kernel#raise
                        45.313k i/100ms
-------------------------------------------------
Custom exception: E2MM#Raise
                         29.005k (± 7.2%) i/s -    145.964k
Custom exception: Kernel#raise
                        589.149k (± 7.8%) i/s -      2.945M

Comparison:
Custom exception: Kernel#raise:   589148.7 i/s
Custom exception: E2MM#Raise:    29004.8 i/s - 20.31x slower

loop vs while true code

$ ruby -v code/general/loop-vs-while-true.rb
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]

Calculating -------------------------------------
          While Loop     1.000  i/100ms
         Kernel loop     1.000  i/100ms
-------------------------------------------------
          While Loop      0.536  (± 0.0%) i/s -      3.000  in   5.593042s
         Kernel loop      0.223  (± 0.0%) i/s -      2.000  in   8.982355s

Comparison:
          While Loop:        0.5 i/s
         Kernel loop:        0.2 i/s - 2.41x slower

ancestors.include? vs <= code

$ ruby -vW0 code/general/inheritance-check.rb
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux]
Warming up --------------------------------------
  less than or equal    66.992k i/100ms
  ancestors.include?    16.943k i/100ms
Calculating -------------------------------------
  less than or equal      1.250M (± 6.4%) i/s -      6.230M in   5.006896s
  ancestors.include?    192.603k (± 4.8%) i/s -    965.751k in   5.025917s

Comparison:
  less than or equal:  1249606.0 i/s
  ancestors.include?:   192602.9 i/s - 6.49x  slower

Method Invocation

call vs send vs method_missing code

$ ruby -v code/method/call-vs-send-vs-method_missing.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
                call   115.094k i/100ms
                send   105.258k i/100ms
      method_missing   100.762k i/100ms
-------------------------------------------------
                call      3.811M (± 5.9%) i/s -     18.991M
                send      3.244M (± 7.2%) i/s -     16.210M
      method_missing      2.729M (± 9.8%) i/s -     13.401M

Comparison:
                call:  3811183.4 i/s
                send:  3244239.1 i/s - 1.17x slower
      method_missing:  2728893.0 i/s - 1.40x slower

Normal way to apply method vs &method(...) code

$ ruby -v code/general/block-apply-method.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
              normal    85.749k i/100ms
             &method    35.529k i/100ms
-------------------------------------------------
              normal      1.867M (± 7.6%) i/s -      9.347M
             &method    467.095k (± 6.4%) i/s -      2.345M

Comparison:
              normal:  1866669.5 i/s
             &method:   467095.4 i/s - 4.00x slower

Function with single Array argument vs splat arguments code

$ ruby -v code/general/array-argument-vs-splat-arguments.rb
ruby 2.1.7p400 (2015-08-18 revision 51632) [x86_64-linux-gnu]
Calculating -------------------------------------
Function with single Array argument
                       157.231k i/100ms
Function with splat arguments
                         4.983k i/100ms
-------------------------------------------------
Function with single Array argument
                          5.581M (± 2.0%) i/s -     27.987M
Function with splat arguments
                         54.428k (± 3.3%) i/s -    274.065k

Comparison:
Function with single Array argument:  5580972.6 i/s
Function with splat arguments:    54427.7 i/s - 102.54x slower

Hash vs OpenStruct on access assuming you already have a Hash or an OpenStruct code

$ ruby -v code/general/hash-vs-openstruct-on-access.rb
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-darwin14]

Calculating -------------------------------------
                Hash   128.344k i/100ms
          OpenStruct   110.723k i/100ms
-------------------------------------------------
                Hash      5.279M (± 7.0%) i/s -     26.311M
          OpenStruct      3.048M (± 7.0%) i/s -     15.169M

Comparison:
                Hash:  5278844.0 i/s
          OpenStruct:  3048139.8 i/s - 1.73x slower

Hash vs OpenStruct (creation) code

$ ruby -v code/general/hash-vs-openstruct.rb
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-darwin14]

Calculating -------------------------------------
                Hash    75.510k i/100ms
          OpenStruct     9.126k i/100ms
-------------------------------------------------
                Hash      1.604M (±11.0%) i/s -      7.929M
          OpenStruct     96.855k (± 9.9%) i/s -    483.678k

Comparison:
                Hash:  1604259.1 i/s
          OpenStruct:    96855.3 i/s - 16.56x slower

Kernel#format vs Float#round().to_s code

$ ruby -v code/general/format-vs-round-and-to-s.rb
ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-darwin15]
Warming up --------------------------------------
         Float#round   106.645k i/100ms
       Kernel#format    84.304k i/100ms
            String#%    78.635k i/100ms
Calculating -------------------------------------
         Float#round      1.570M (± 3.2%) i/s - 7.892M in   5.030672s
       Kernel#format      1.144M (± 3.0%) i/s - 5.733M in   5.015621s
            String#%      1.047M (± 4.2%) i/s - 5.269M in   5.042970s

Comparison:
         Float#round:  1570411.4 i/s
       Kernel#format:  1144036.6 i/s - 1.37x  slower
            String#%:  1046689.1 i/s - 1.50x  slower

Array

Array#bsearch vs Array#find code

WARNING: bsearch ONLY works on sorted array. More details please see #29.

$ ruby -v code/array/bsearch-vs-find.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
                find     1.000  i/100ms
             bsearch    42.216k i/100ms
-------------------------------------------------
                find      0.184  (± 0.0%) i/s -      1.000  in   5.434758s
             bsearch    577.301k (± 6.6%) i/s -      2.913M

Comparison:
             bsearch:   577300.7 i/s
                find:        0.2 i/s - 3137489.63x slower

Array#length vs Array#size vs Array#count code

Use #length when you only want to know how many elements in the array, #count could also achieve this. However #count should be use for counting specific elements in array. Note #size is an alias of #length.

$ ruby -v code/array/length-vs-size-vs-count.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
        Array#length   172.998k i/100ms
          Array#size   168.130k i/100ms
         Array#count   164.911k i/100ms
-------------------------------------------------
        Array#length     11.394M (± 6.1%) i/s -     56.743M
          Array#size     11.303M (± 6.5%) i/s -     56.324M
         Array#count      9.195M (± 8.6%) i/s -     45.680M

Comparison:
        Array#length: 11394036.7 i/s
          Array#size: 11302701.1 i/s - 1.01x slower
         Array#count:  9194976.2 i/s - 1.24x slower

Array#shuffle.first vs Array#sample code

Array#shuffle allocates an extra array. Array#sample indexes into the array without allocating an extra array. This is the reason why Array#sample exists. —— @sferik rails/rails#17245

$ ruby -v code/array/shuffle-first-vs-sample.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
 Array#shuffle.first    25.406k i/100ms
        Array#sample   125.101k i/100ms
-------------------------------------------------
 Array#shuffle.first    304.341k (± 4.3%) i/s -      1.524M
        Array#sample      5.727M (± 8.6%) i/s -     28.523M

Comparison:
        Array#sample:  5727032.0 i/s
 Array#shuffle.first:   304341.1 i/s - 18.82x slower

Array#[](0) vs Array#first code

$ ruby -v code/array/array-first-vs-index.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
           Array#[0]   152.751k i/100ms
         Array#first   148.088k i/100ms
-------------------------------------------------
           Array#[0]      8.614M (± 7.0%) i/s -     42.923M
         Array#first      7.465M (±10.7%) i/s -     36.874M

Comparison:
           Array#[0]:  8613583.7 i/s
         Array#first:  7464526.6 i/s - 1.15x slower

Array#[](-1) vs Array#last code

$ ruby -v code/array/array-last-vs-index.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
            Array#[-1]   151.940k i/100ms
          Array#last   153.371k i/100ms
-------------------------------------------------
            Array#[-1]      8.582M (± 4.6%) i/s -     42.847M
          Array#last      7.639M (± 5.7%) i/s -     38.189M

Comparison:
            Array#[-1]:  8582074.3 i/s
          Array#last:  7639254.5 i/s - 1.12x slower

Array#insert vs Array#unshift code

$ ruby -v code/array/insert-vs-unshift.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin10.0]
Calculating -------------------------------------
       Array#unshift     4.000  i/100ms
        Array#insert     1.000  i/100ms
-------------------------------------------------
       Array#unshift     44.947  (± 6.7%) i/s -    224.000
        Array#insert      0.171  (± 0.0%) i/s -      1.000  in   5.841595s

Comparison:
       Array#unshift:       44.9 i/s
        Array#insert:        0.2 i/s - 262.56x slower

Array#concat vs Array#+ code

Array#+ returns a new array built by concatenating the two arrays together to produce a third array. Array#concat appends the elements of the other array to self. This means that the + operator will create a new array each time it is called (which is expensive), while concat only appends the new element.

$ ruby -v code/array/array-concat-vs-+.rb
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin18]
Warming up --------------------------------------
        Array#concat    23.000  i/100ms
             Array#+     1.000  i/100ms
Calculating -------------------------------------
        Array#concat    217.669  (±15.2%) i/s -      1.058k in   5.016952s
             Array#+      1.475  (± 0.0%) i/s -      8.000  in   5.467642s

Comparison:
        Array#concat:      217.7 i/s
             Array#+:        1.5 i/s - 147.54x  slower

Array#new vs Fixnum#times + map code

Typical slowdown is 40-60% depending on the size of the array. See the corresponding pull request for performance characteristics.

ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]
Calculating -------------------------------------
           Array#new    63.875k i/100ms
  Fixnum#times + map    48.010k i/100ms
-------------------------------------------------
           Array#new      1.070M (± 2.2%) i/s -      5.365M
  Fixnum#times + map    678.097k (± 2.7%) i/s -      3.409M

Comparison:
           Array#new:  1069837.0 i/s
  Fixnum#times + map:   678097.4 i/s - 1.58x slower

Array#sort.reverse vs Array#sort_by + block code

$ ruby -v code/array/sort-reverse-vs-sort_by.rb
ruby 2.5.2p104 (2018-10-18 revision 65133) [x86_64-darwin13]
Warming up --------------------------------------
Array#sort.reverse
                        16.231k i/100ms
Array#sort_by &:-@
                         5.406k i/100ms
Calculating -------------------------------------
Array#sort.reverse
                        149.492k (±11.0%) i/s -    746.626k in   5.070375s
Array#sort_by &:-@
                         51.981k (± 8.8%) i/s -    259.488k in   5.041625s

Comparison:
Array#sort.reverse:   149492.2 i/s
Array#sort_by &:-@:    51980.6 i/s - 2.88x  (± 0.00) slower

Enumerable

Enumerable#each + push vs Enumerable#map code

$ ruby -v code/enumerable/each-push-vs-map.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
   Array#each + push     9.025k i/100ms
           Array#map    13.947k i/100ms
-------------------------------------------------
   Array#each + push     99.634k (± 3.2%) i/s -    505.400k
           Array#map    158.091k (± 4.2%) i/s -    794.979k

Comparison:
           Array#map:   158090.9 i/s
   Array#each + push:    99634.2 i/s - 1.59x slower

Enumerable#each vs for loop code

$ ruby -v code/enumerable/each-vs-for-loop.rb
ruby 2.2.0preview1 (2014-09-17 trunk 47616) [x86_64-darwin14]

Calculating -------------------------------------
            For loop    17.111k i/100ms
               #each    18.464k i/100ms
-------------------------------------------------
            For loop    198.517k (± 5.3%) i/s -    992.438k
               #each    208.157k (± 5.0%) i/s -      1.052M

Comparison:
               #each:   208157.4 i/s
            For loop:   198517.3 i/s - 1.05x slower

Enumerable#each_with_index vs while loop code

rails/rails#12065

$ ruby -v code/enumerable/each_with_index-vs-while-loop.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
          While Loop    22.553k i/100ms
     each_with_index    11.963k i/100ms
-------------------------------------------------
          While Loop    240.752k (± 7.1%) i/s -      1.218M
     each_with_index    126.753k (± 5.9%) i/s -    634.039k

Comparison:
          While Loop:   240752.1 i/s
     each_with_index:   126753.4 i/s - 1.90x slower

Enumerable#map...Array#flatten vs Enumerable#flat_map code

-- @sferik rails/rails@3413b88, Replace map.flatten with flat_map, Replace map.flatten(1) with flat_map

$ ruby -v code/enumerable/map-flatten-vs-flat_map.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
Array#map.flatten(1)     3.315k i/100ms
   Array#map.flatten     3.283k i/100ms
      Array#flat_map     5.350k i/100ms
-------------------------------------------------
Array#map.flatten(1)     33.801k (± 4.3%) i/s -    169.065k
   Array#map.flatten     34.530k (± 6.0%) i/s -    173.999k
      Array#flat_map     55.980k (± 5.0%) i/s -    283.550k

Comparison:
      Array#flat_map:    55979.6 i/s
   Array#map.flatten:    34529.6 i/s - 1.62x slower
Array#map.flatten(1):    33800.6 i/s - 1.66x slower

Enumerable#reverse.each vs Enumerable#reverse_each code

Enumerable#reverse allocates an extra array. Enumerable#reverse_each yields each value without allocating an extra array. This is the reason why Enumerable#reverse_each exists. -- @sferik rails/rails#17244

$ ruby -v code/enumerable/reverse-each-vs-reverse_each.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
  Array#reverse.each    16.746k i/100ms
  Array#reverse_each    18.590k i/100ms
-------------------------------------------------
  Array#reverse.each    190.729k (± 4.8%) i/s -    954.522k
  Array#reverse_each    216.060k (± 4.3%) i/s -      1.078M

Comparison:
  Array#reverse_each:   216060.5 i/s
  Array#reverse.each:   190729.1 i/s - 1.13x slower

Enumerable#sort_by.first vs Enumerable#min_by code

Enumerable#sort_by performs a sort of the enumerable and allocates a new array the size of the enumerable. Enumerable#min_by doesn't perform a sort or allocate an array the size of the enumerable. Similar comparisons hold for Enumerable#sort_by.last vs Enumerable#max_by, Enumerable#sort.first vs Enumerable#min, and Enumerable#sort.last vs Enumerable#max.

$ ruby -v code/enumerable/sort_by-first-vs-min_by.rb
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin17]
Warming up --------------------------------------
   Enumerable#min_by    15.170k i/100ms
Enumerable#sort_by...first
                        10.413k i/100ms
Calculating -------------------------------------
   Enumerable#min_by    157.877k (± 0.9%) i/s -    804.010k in   5.093048s
Enumerable#sort_by...first
                        106.831k (± 1.3%) i/s -    541.476k in   5.069403s

Comparison:
   Enumerable#min_by:   157877.0 i/s
Enumerable#sort_by...first:   106831.1 i/s - 1.48x  slower

Enumerable#detect vs Enumerable#select.first code

$ ruby -v code/enumerable/select-first-vs-detect.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
Enumerable#select.first  8.515k i/100ms
   Enumerable#detect    33.885k i/100ms
-------------------------------------------------
Enumerable#select.first  89.757k (± 5.0%) i/s -      1.797M
   Enumerable#detect    434.304k (± 5.2%) i/s -      8.675M

Comparison:
   Enumerable#detect:   434304.2 i/s
Enumerable#select.first:    89757.4 i/s - 4.84x slower

Enumerable#select.last vs Enumerable#reverse.detect code

$ ruby -v code/enumerable/select-last-vs-reverse-detect.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
Enumerable#reverse.detect 62.636k i/100ms
Enumerable#select.last    11.687k i/100ms
-------------------------------------------------
Enumerable#reverse.detect 1.263M (± 8.2%) i/s -      6.326M
Enumerable#select.last  119.387k (± 5.7%) i/s -    596.037k

Comparison:
Enumerable#reverse.detect:  1263100.2 i/s
Enumerable#select.last:     119386.8 i/s - 10.58x slower

Enumerable#sort vs Enumerable#sort_by code

$ ruby -v code/enumerable/sort-vs-sort_by.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
Enumerable#sort_by (Symbol#to_proc) 2.680k i/100ms
  Enumerable#sort_by                2.462k i/100ms
     Enumerable#sort                1.320k i/100ms
-------------------------------------------------
Enumerable#sort_by (Symbol#to_proc) 25.916k (± 4.4%) i/s -    131.320k
  Enumerable#sort_by                24.650k (± 5.1%) i/s -    125.562k
     Enumerable#sort                14.018k (± 5.6%) i/s -     69.960k

Comparison:
Enumerable#sort_by (Symbol#to_proc):    25916.1 i/s
  Enumerable#sort_by:                   24650.2 i/s - 1.05x slower
     Enumerable#sort:                   14018.3 i/s - 1.85x slower

Enumerable#inject Symbol vs Enumerable#inject Proc code

Of note, to_proc for 1.8.7 is considerable slower than the block format

$ ruby -v code/enumerable/inject-symbol-vs-block.rb
ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-darwin14]
Warming up --------------------------------------
       inject symbol     1.893k i/100ms
      inject to_proc     1.583k i/100ms
        inject block     1.390k i/100ms
Calculating -------------------------------------
       inject symbol     19.001k (± 3.8%) i/s -     96.543k
      inject to_proc     15.958k (± 3.5%) i/s -     80.733k
        inject block     14.063k (± 3.9%) i/s -     70.890k

Comparison:
       inject symbol:    19001.5 i/s
      inject to_proc:    15958.3 i/s - 1.19x slower
        inject block:    14063.1 i/s - 1.35x slower

Date

Date.iso8601 vs Date.parse code

When expecting well-formatted data from e.g. an API, iso8601 is faster and will raise an ArgumentError on malformed input.

$ ruby -v code/date/iso8601-vs-parse.rb
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]
Warming up --------------------------------------
        Date.iso8601    28.880k i/100ms
          Date.parse    15.805k i/100ms
Calculating -------------------------------------
        Date.iso8601    328.035k (± 4.7%) i/s -      1.646M in   5.029287s
          Date.parse    175.546k (± 3.8%) i/s -    885.080k in   5.049444s

Comparison:
        Date.iso8601:   328035.3 i/s
          Date.parse:   175545.9 i/s - 1.87x  slower

Hash

Hash#[] vs Hash#fetch code

If you use Ruby 2.2, Symbol could be more performant than String as Hash keys. Read more regarding this: Symbol GC in Ruby 2.2 and Unraveling String Key Performance in Ruby 2.2.

$ ruby -v code/hash/bracket-vs-fetch.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
     Hash#[], symbol   143.850k i/100ms
  Hash#fetch, symbol   137.425k i/100ms
     Hash#[], string   143.083k i/100ms
  Hash#fetch, string   120.417k i/100ms
-------------------------------------------------
     Hash#[], symbol      7.531M (± 6.6%) i/s -     37.545M
  Hash#fetch, symbol      6.644M (± 8.2%) i/s -     32.982M
     Hash#[], string      6.657M (± 7.7%) i/s -     33.195M
  Hash#fetch, string      3.981M (± 8.7%) i/s -     19.748M

Comparison:
     Hash#[], symbol:  7531355.8 i/s
     Hash#[], string:  6656818.8 i/s - 1.13x slower
  Hash#fetch, symbol:  6643665.5 i/s - 1.13x slower
  Hash#fetch, string:  3981166.5 i/s - 1.89x slower

Hash#dig vs Hash#[] vs Hash#fetch code

Ruby 2.3 introduced Hash#dig which is a readable and performant option for retrieval from a nested hash, returning nil if an extraction step fails. See #102 (comment) for more info.

$ ruby -v code/hash/dig-vs-\[\]-vs-fetch.rb
ruby 2.3.0p0 (2015-12-25 revision 53290) [x86_64-darwin15]

Calculating -------------------------------------
            Hash#dig      5.719M (± 6.1%) i/s -     28.573M in   5.013997s
             Hash#[]      6.066M (± 6.9%) i/s -     30.324M in   5.025614s
          Hash#[] ||      5.366M (± 6.5%) i/s -     26.933M in   5.041403s
          Hash#[] &&      2.782M (± 4.8%) i/s -     13.905M in   5.010328s
          Hash#fetch      4.101M (± 6.1%) i/s -     20.531M in   5.024945s
 Hash#fetch fallback      2.975M (± 5.5%) i/s -     14.972M in   5.048880s

Comparison:
             Hash#[]:  6065791.0 i/s
            Hash#dig:  5719290.9 i/s - same-ish: difference falls within error
          Hash#[] ||:  5366226.5 i/s - same-ish: difference falls within error
          Hash#fetch:  4101102.1 i/s - 1.48x slower
 Hash#fetch fallback:  2974906.9 i/s - 2.04x slower
          Hash#[] &&:  2781646.6 i/s - 2.18x slower

Hash[] vs Hash#dup code

Source: http://tenderlovemaking.com/2015/02/11/weird-stuff-with-hashes.html

Does this mean that you should switch to Hash[]? Only if your benchmarks can prove that it’s a bottleneck. Please please please don’t change all of your code because this shows it’s faster. Make sure to measure your app performance first.

$ ruby -v code/hash/bracket-vs-dup.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
              Hash[]    29.403k i/100ms
            Hash#dup    16.195k i/100ms
-------------------------------------------------
              Hash[]    343.987k (± 8.7%) i/s -      1.735M
            Hash#dup    163.516k (±10.2%) i/s -    825.945k

Comparison:
              Hash[]:   343986.5 i/s
            Hash#dup:   163516.3 i/s - 2.10x slower

Hash#fetch with argument vs Hash#fetch + block code

Note that the speedup in the block version comes from avoiding repeated construction of the argument. If the argument is a constant, number symbol or something of that sort the argument version is actually slightly faster See also #39 (comment)

$ ruby -v code/hash/fetch-vs-fetch-with-block.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin13]
Calculating -------------------------------------
  Hash#fetch + const   129.868k i/100ms
  Hash#fetch + block   125.254k i/100ms
    Hash#fetch + arg   121.155k i/100ms
-------------------------------------------------
  Hash#fetch + const      7.031M (± 7.0%) i/s -     34.934M
  Hash#fetch + block      6.815M (± 4.2%) i/s -     34.069M
    Hash#fetch + arg      4.753M (± 5.6%) i/s -     23.746M

Comparison:
  Hash#fetch + const:  7030600.4 i/s
  Hash#fetch + block:  6814826.7 i/s - 1.03x slower
    Hash#fetch + arg:  4752567.2 i/s - 1.48x slower

Hash#each_key instead of Hash#keys.each code

Hash#keys.each allocates an array of keys; Hash#each_key iterates through the keys without allocating a new array. This is the reason why Hash#each_key exists. —— @sferik rails/rails#17099

$ ruby -v code/hash/keys-each-vs-each_key.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
      Hash#keys.each    56.690k i/100ms
       Hash#each_key    59.658k i/100ms
-------------------------------------------------
      Hash#keys.each    869.262k (± 5.0%) i/s -      4.365M
       Hash#each_key      1.049M (± 6.0%) i/s -      5.250M

Comparison:
       Hash#each_key:  1049161.6 i/s
      Hash#keys.each:   869262.3 i/s - 1.21x slower

Hash#key? instead of Hash#keys.include? code

Hash#keys.include? allocates an array of keys and performs an O(n) search; Hash#key? performs an O(1) hash lookup without allocating a new array.

$ ruby -v code/hash/keys-include-vs-key.rb
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin17]

Calculating -------------------------------------
  Hash#keys.include?      8.612k (± 2.5%) i/s -     43.248k in   5.024749s
           Hash#key?      6.366M (± 5.5%) i/s -     31.715M in   5.002276s

Comparison:
           Hash#key?:  6365855.5 i/s
  Hash#keys.include?:     8612.4 i/s - 739.15x  slower

Hash#value? instead of Hash#values.include? code

Hash#values.include? allocates an array of values and performs an O(n) search; Hash#value? performs an O(n) search without allocating a new array.

$ ruby -v code/hash/values-include-vs-value.rb
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin17]

Calculating -------------------------------------
Hash#values.include?     23.187k (± 4.3%) i/s -    117.720k in   5.086976s
         Hash#value?     38.395k (± 1.0%) i/s -    194.361k in   5.062696s

Comparison:
         Hash#value?:    38395.0 i/s
Hash#values.include?:    23186.8 i/s - 1.66x  slower

Hash#merge! vs Hash#[]= code

$ ruby -v code/hash/merge-bang-vs-\[\]=.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
         Hash#merge!     1.023k i/100ms
            Hash#[]=     2.844k i/100ms
-------------------------------------------------
         Hash#merge!     10.653k (± 4.9%) i/s -     53.196k
            Hash#[]=     28.287k (±12.4%) i/s -    142.200k

Comparison:
            Hash#[]=:    28287.1 i/s
         Hash#merge!:    10653.3 i/s - 2.66x slower

Hash#update vs Hash#[]= code

$ ruby -v code/hash/update-vs-\[\]=.rb
ruby 2.6.6p146 (2020-03-31 revision 67876) [x86_64-darwin18]

Warming up --------------------------------------
            Hash#[]=     7.453k i/100ms
         Hash#update     4.311k i/100ms
Calculating -------------------------------------
            Hash#[]=     74.764k (± 1.9%) i/s -    380.103k in   5.085962s
         Hash#update     43.220k (± 0.8%) i/s -    219.861k in   5.087364s

Comparison:
            Hash#[]=:    74764.0 i/s
         Hash#update:    43220.1 i/s - 1.73x  (± 0.00) slower

Hash#merge vs Hash#**other code

$ ruby -v code/hash/merge-vs-double-splat-operator.rb
ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-darwin15]
Warming up --------------------------------------
        Hash#**other    64.624k i/100ms
          Hash#merge    38.827k i/100ms
Calculating -------------------------------------
        Hash#**other    798.397k (± 6.9%) i/s -      4.007M in   5.053516s
          Hash#merge    434.171k (± 4.5%) i/s -      2.174M in   5.018927s

Comparison:
        Hash#**other:   798396.6 i/s
          Hash#merge:   434170.8 i/s - 1.84x  slower

Hash#merge vs Hash#merge! code

$ ruby -v code/hash/merge-vs-merge-bang.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
          Hash#merge    39.000  i/100ms
         Hash#merge!     1.008k i/100ms
-------------------------------------------------
          Hash#merge    409.610  (± 7.6%) i/s -      2.067k
         Hash#merge!      9.830k (± 5.8%) i/s -     49.392k

Comparison:
         Hash#merge!:     9830.3 i/s
          Hash#merge:      409.6 i/s - 24.00x slower

{}#merge!(Hash) vs Hash#merge({}) vs Hash#dup#merge!({}) code

When we don't want to modify the original hash, and we want duplicates to be created See #42 for more details.

$ ruby -v code/hash/merge-bang-vs-merge-vs-dup-merge-bang.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-linux]

Calculating -------------------------------------
{}#merge!(Hash) do end     2.006k i/100ms
        Hash#merge({})   762.000  i/100ms
   Hash#dup#merge!({})   736.000  i/100ms
-------------------------------------------------
{}#merge!(Hash) do end     20.055k (± 2.0%) i/s -    100.300k in   5.003322s
        Hash#merge({})      7.676k (± 1.2%) i/s -     38.862k in   5.063382s
   Hash#dup#merge!({})      7.440k (± 1.1%) i/s -     37.536k in   5.045851s

Comparison:
{}#merge!(Hash) do end:    20054.8 i/s
        Hash#merge({}):     7676.3 i/s - 2.61x slower
   Hash#dup#merge!({}):     7439.9 i/s - 2.70x slower

Hash#sort_by vs Hash#sort code

To sort hash by key.

$ ruby -v code/hash/hash-key-sort_by-vs-sort.rb
ruby 2.2.1p85 (2015-02-26 revision 49769) [x86_64-darwin14]

Calculating -------------------------------------
      sort_by + to_h    11.468k i/100ms
         sort + to_h     8.107k i/100ms
-------------------------------------------------
      sort_by + to_h    122.176k (± 6.0%) i/s -    619.272k
         sort + to_h     81.973k (± 4.7%) i/s -    413.457k

Comparison:
      sort_by + to_h:   122176.2 i/s
         sort + to_h:    81972.8 i/s - 1.49x slower

Native Hash#slice vs other slice implementations before native code

Since ruby 2.5, Hash comes with a slice method to select hash members by keys.

$ ruby -v code/hash/slice-native-vs-before-native.rb
ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-linux]
Warming up --------------------------------------
Hash#native-slice      178.077k i/100ms
Array#each             124.311k i/100ms
Array#each_w/_object   110.818k i/100ms
Hash#select-include     66.972k i/100ms
Calculating -------------------------------------
Hash#native-slice         2.540M (± 1.5%) i/s -     12.822M in   5.049955s
Array#each                1.614M (± 1.0%) i/s -      8.080M in   5.007925s
Array#each_w/_object      1.353M (± 2.6%) i/s -      6.760M in   5.000441s
Hash#select-include     760.944k (± 0.9%) i/s -      3.817M in   5.017123s

Comparison:
Hash#native-slice   :  2539515.5 i/s
Array#each          :  1613665.5 i/s - 1.57x  slower
Array#each_w/_object:  1352851.8 i/s - 1.88x  slower
Hash#select-include :   760944.2 i/s - 3.34x  slower

Proc & Block

Block vs Symbol#to_proc code

Symbol#to_proc is considerably more concise than using block syntax. ...In some cases, it reduces the number of lines of code. —— @sferik rails/rails#16833

$ ruby -v code/proc-and-block/block-vs-to_proc.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
               Block     4.632k i/100ms
      Symbol#to_proc     5.225k i/100ms
-------------------------------------------------
               Block     47.914k (± 6.3%) i/s -    240.864k
      Symbol#to_proc     54.791k (± 4.1%) i/s -    276.925k

Comparison:
      Symbol#to_proc:    54791.1 i/s
               Block:    47914.3 i/s - 1.14x slower

Proc#call and block arguments vs yield code

In MRI Ruby before 2.5, block arguments are converted to Procs, which incurs a heap allocation.

$ ruby -v code/proc-and-block/proc-call-vs-yield.rb
ruby 2.4.4p296 (2018-03-28 revision 63013) [x86_64-darwin18]
Calculating -------------------------------------
        block.call      1.967M (± 2.0%) i/s -      9.871M in   5.019328s
     block + yield      2.147M (± 3.3%) i/s -     10.814M in   5.044319s
      unused block      2.265M (± 1.9%) i/s -     11.333M in   5.004522s
             yield     10.436M (± 1.6%) i/s -     52.260M in   5.008851s

Comparison:
             yield: 10436414.0 i/s
      unused block:  2265399.0 i/s - 4.61x  slower
     block + yield:  2146619.0 i/s - 4.86x  slower
        block.call:  1967300.9 i/s - 5.30x  slower

MRI Ruby 2.5 implements Lazy Proc allocation for block parameters, which speeds things up by about 3x.:

$ ruby -v code/proc-and-block/proc-call-vs-yield.rb
ruby 2.5.3p105 (2018-10-18 revision 65156) [x86_64-darwin18]
Calculating -------------------------------------
        block.call      1.970M (± 2.3%) i/s -      9.863M in   5.009599s
     block + yield      9.075M (± 2.6%) i/s -     45.510M in   5.018369s
      unused block     11.176M (± 2.7%) i/s -     55.977M in   5.012741s
             yield     10.588M (± 1.9%) i/s -     53.108M in   5.017755s

Comparison:
      unused block: 11176355.0 i/s
             yield: 10588342.3 i/s - 1.06x  slower
     block + yield:  9075355.5 i/s - 1.23x  slower
        block.call:  1969834.0 i/s - 5.67x  slower

MRI Ruby 2.6 implements an optimization for block.call where a block parameter is passed:

$ ruby -v code/proc-and-block/proc-call-vs-yield.rb
ruby 2.6.1p33 (2019-01-30 revision 66950) [x86_64-darwin18]
Calculating -------------------------------------
        block.call     10.587M (± 1.2%) i/s -     52.969M in   5.003808s
     block + yield     12.630M (± 0.3%) i/s -     63.415M in   5.020910s
      unused block     15.981M (± 0.8%) i/s -     80.255M in   5.022305s
             yield     15.352M (± 3.1%) i/s -     76.816M in   5.009404s

Comparison:
      unused block: 15980789.4 i/s
             yield: 15351931.0 i/s - 1.04x  slower
     block + yield: 12630378.1 i/s - 1.27x  slower
        block.call: 10587315.1 i/s - 1.51x  slower

String

String#dup vs String#+ code

Note that String.new is not the same as the options compared, since it is always ASCII-8BIT encoded instead of the script encoding (usually UTF-8).

$ ruby -v code/string/dup-vs-unary-plus.rb
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]

Calculating -------------------------------------
           String#+@      7.697M (± 1.4%) i/s -     38.634M in   5.020313s
          String#dup      3.566M (± 1.0%) i/s -     17.860M in   5.008377s

Comparison:
           String#+@:  7697108.3 i/s
          String#dup:  3566485.7 i/s - 2.16x  slower

String#casecmp vs String#casecmp? vs String#downcase + == code

String#casecmp? is available on Ruby 2.4 or later. Note that String#casecmp only works on characters A-Z/a-z, not all of Unicode.

$ ruby -v code/string/casecmp-vs-downcase-\=\=.rb
ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin19]
Warming up --------------------------------------
     String#casecmp?   395.796k i/100ms
String#downcase + ==   543.958k i/100ms
      String#casecmp   730.028k i/100ms
Calculating -------------------------------------
     String#casecmp?      3.687M (±10.9%) i/s -     18.602M in   5.158065s
String#downcase + ==      5.017M (±11.3%) i/s -     25.022M in   5.089175s
      String#casecmp      6.948M (± 6.0%) i/s -     35.041M in   5.062714s

Comparison:
      String#casecmp:  6948231.0 i/s
String#downcase + ==:  5017089.5 i/s - 1.38x  (± 0.00) slower
     String#casecmp?:  3686650.7 i/s - 1.88x  (± 0.00) slower

String Concatenation code

$ ruby -v code/string/concatenation.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-linux]

Warming up --------------------------------------
            String#+   149.298k i/100ms
       String#concat   151.505k i/100ms
       String#append   153.389k i/100ms
         "foo" "bar"   195.552k i/100ms
  "#{'foo'}#{'bar'}"   193.784k i/100ms
Calculating -------------------------------------
            String#+      2.977M (± 1.1%) i/s -     14.930M in   5.015179s
       String#concat      3.017M (± 1.3%) i/s -     15.150M in   5.023063s
       String#append      3.076M (± 1.2%) i/s -     15.492M in   5.037683s
         "foo" "bar"      5.370M (± 1.0%) i/s -     26.986M in   5.026271s
  "#{'foo'}#{'bar'}"      5.182M (± 4.6%) i/s -     25.967M in   5.022093s

Comparison:
         "foo" "bar":  5369594.5 i/s
  "#{'foo'}#{'bar'}":  5181745.7 i/s - same-ish: difference falls within error
       String#append:  3075719.2 i/s - 1.75x slower
       String#concat:  3016703.5 i/s - 1.78x slower
            String#+:  2977282.7 i/s - 1.80x slower

String#match vs String.match? vs String#start_with?/String#end_with? code (start) code (end)

The regular expression approaches become slower as the tested string becomes longer. For short strings, String#match? performs similarly to String#start_with?/String#end_with?.

:warning: Sometimes you cant replace regexp with start_with?, for example: "a\nb" =~ /^b/ #=> 2 but "a\nb" =~ /\Ab/ #=> nil. :warning:

$ ruby -v code/string/start-string-checking-match-vs-start_with.rb
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]

Calculating -------------------------------------
           String#=~      1.088M (± 4.0%) i/s -      5.471M in   5.034404s
       String#match?      5.138M (± 5.0%) i/s -     25.669M in   5.008810s
  String#start_with?      6.314M (± 4.3%) i/s -     31.554M in   5.007207s

Comparison:
  String#start_with?:  6314182.0 i/s
       String#match?:  5138115.1 i/s - 1.23x  slower
           String#=~:  1088461.5 i/s - 5.80x  slower

$ ruby -v code/string/end-string-checking-match-vs-end_with.rb
  ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]

  Calculating -------------------------------------
             String#=~    918.101k (± 6.0%) i/s -      4.650M in   5.084079s
         String#match?      3.009M (± 6.8%) i/s -     14.991M in   5.005691s
      String#end_with?      4.548M (± 9.3%) i/s -     22.684M in   5.034115s

  Comparison:
      String#end_with?:  4547871.0 i/s
         String#match?:  3008554.5 i/s - 1.51x  slower
             String#=~:   918100.5 i/s - 4.95x  slower

String#start_with? vs String#[].== code

$ ruby -v code/string/end-string-checking-match-vs-end_with.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
  String#start_with?      2.047M (± 4.5%) i/s -     10.242M in   5.015146s
    String#[0, n] ==    711.802k (± 7.3%) i/s -      3.551M in   5.019543s
   String#[RANGE] ==    651.751k (± 6.2%) i/s -      3.296M in   5.078772s
   String#[0...n] ==    427.207k (± 5.7%) i/s -      2.136M in   5.019245s

Comparison:
  String#start_with?:  2046618.9 i/s
    String#[0, n] ==:   711802.3 i/s - 2.88x slower
   String#[RANGE] ==:   651751.2 i/s - 3.14x slower
   String#[0...n] ==:   427206.8 i/s - 4.79x slower

Regexp#=== vs Regexp#match vs Regexp#match? vs String#match vs String#=~ vs String#match? code

String#match? and Regexp#match? are available on Ruby 2.4 or later. ActiveSupport provides a forward compatible extension of Regexp for older Rubies without the speed improvement.

:warning: Sometimes you can't replace match with match?, This is only useful for cases where you are checking for a match and not using the resultant match object. :warning: Regexp#=== is also faster than String#match but you need to switch the order of arguments.

$ ruby -v code/string/===-vs-=~-vs-match.rb
ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]
Calculating -------------------------------------
       Regexp#match?      6.994M (± 3.0%) i/s -     35.144M in   5.029647s
       String#match?      6.909M (± 3.3%) i/s -     34.663M in   5.023177s
           String#=~      2.784M (± 5.2%) i/s -     13.996M in   5.043168s
          Regexp#===      2.702M (± 4.5%) i/s -     13.631M in   5.056215s
        Regexp#match      2.607M (± 4.9%) i/s -     13.025M in   5.009071s
        String#match      2.362M (± 5.7%) i/s -     11.817M in   5.020344s

Comparison:
       Regexp#match?:  6994107.7 i/s
       String#match?:  6909055.7 i/s - same-ish: difference falls within error
           String#=~:  2783577.8 i/s - 2.51x  slower
          Regexp#===:  2702030.0 i/s - 2.59x  slower
        Regexp#match:  2607484.0 i/s - 2.68x  slower
        String#match:  2362314.8 i/s - 2.96x  slower

See #59 and #62 for discussions.

String#gsub vs String#sub vs String#[]= code

$ ruby -v code/string/gsub-vs-sub.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-linux]

Warming up --------------------------------------
         String#gsub    48.360k i/100ms
          String#sub    45.739k i/100ms
String#dup["string"]=   59.896k i/100ms
Calculating -------------------------------------
         String#gsub    647.666k (± 3.3%) i/s -      3.240M in   5.008504s
          String#sub    756.665k (± 2.0%) i/s -      3.796M in   5.019235s
String#dup["string"]=   917.873k (± 1.8%) i/s -      4.612M in   5.026253s

Comparison:
String#dup["string"]=:   917873.1 i/s
          String#sub:    756664.7 i/s - 1.21x slower
         String#gsub:    647665.6 i/s - 1.42x slower

String#gsub vs String#tr code

rails/rails#17257

$ ruby -v code/string/gsub-vs-tr.rb
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]

Calculating -------------------------------------
         String#gsub    38.268k i/100ms
           String#tr    83.210k i/100ms
-------------------------------------------------
         String#gsub    516.604k (± 4.4%) i/s -      2.602M
           String#tr      1.862M (± 4.0%) i/s -      9.320M

Comparison:
           String#tr:  1861860.4 i/s
         String#gsub:   516604.2 i/s - 3.60x slower

String#gsub vs String#tr vs String#delete code

ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-linux]

Calculating -------------------------------------
         String#gsub      1.342M (± 1.3%) i/s -      6.816M in   5.079675s
           String#tr      2.627M (± 1.0%) i/s -     13.387M in   5.096083s
       String#delete      2.924M (± 0.7%) i/s -     14.889M in   5.093070s
 String#delete const      3.136M (± 2.6%) i/s -     15.866M in   5.064043s

Comparison:
 String#delete const:  3135559.1 i/s
       String#delete:  2923531.8 i/s - 1.07x  slower
           String#tr:  2627150.5 i/s - 1.19x  slower
         String#gsub:  1342013.4 i/s - 2.34x  slower

Mutable vs Immutable code

$ ruby -v code/string/mutable_vs_immutable_strings.rb
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin14]

Calculating -------------------------------------
      Without Freeze      7.279M (± 6.6%) i/s -     36.451M in   5.029785s
         With Freeze      9.329M (± 7.9%) i/s -     46.370M in   5.001345s

Comparison:
         With Freeze:  9329054.3 i/s
      Without Freeze:  7279203.1 i/s - 1.28x slower

String#sub! vs String#gsub! vs String#[]= code

Note that String#[] will throw an IndexError when given string or regexp not matched.

$ ruby -v code/string/sub\!-vs-gsub\!-vs-\[\]\=.rb
ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]

Calculating -------------------------------------
  String#['string']=    74.512k i/100ms
 String#sub!'string'    52.801k i/100ms
String#gsub!'string'    34.480k i/100ms
  String#[/regexp/]=    55.325k i/100ms
 String#sub!/regexp/    45.770k i/100ms
String#gsub!/regexp/    27.665k i/100ms
-------------------------------------------------
  String#['string']=      1.215M (± 6.2%) i/s -      6.110M
 String#sub!'string'    752.731k (± 6.2%) i/s -      3.749M
String#gsub!'string'    481.183k (± 4.4%) i/s -      2.414M
  String#[/regexp/]=    840.615k (± 5.3%) i/s -      4.205M
 String#sub!/regexp/    663.075k (± 7.8%) i/s -      3.295M
String#gsub!/regexp/    342.004k (± 7.5%) i/s -      1.715M

Comparison:
  String#['string']=:  1214845.5 i/s
  String#[/regexp/]=:   840615.2 i/s - 1.45x slower
 String#sub!'string':   752731.4 i/s - 1.61x slower
 String#sub!/regexp/:   663075.3 i/s - 1.83x slower
String#gsub!'string':   481183.5 i/s - 2.52x slower
String#gsub!/regexp/:   342003.8 i/s - 3.55x slower

String#sub vs String#delete_prefix code

Ruby 2.5 introduced String#delete_prefix. Note that this can only be used for removing characters from the start of a string.

$ ruby -v code/string/sub-vs-delete_prefix.rb
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-darwin17]
Calculating -------------------------------------
String#delete_prefix      4.112M (± 1.8%) i/s -     20.707M in   5.037928s
          String#sub    814.725k (± 1.4%) i/s -      4.088M in   5.018962s

Comparison:
String#delete_prefix:  4111531.1 i/s
          String#sub:   814725.3 i/s - 5.05x  slower

String#sub vs String#chomp vs String#delete_suffix code

Ruby 2.5 introduced String#delete_suffix as a counterpart to delete_prefix. The performance gain over chomp is small and during some runs the difference falls within the error margin. Note that this can only be used for removing characters from the end of a string.

$ ruby -v code/string/sub-vs-chomp-vs-delete_suffix.rb
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-darwin17]
Calculating -------------------------------------
        String#sub    838.415k (± 1.7%) i/s -      4.214M in   5.027412s
      String#chomp      3.951M (± 2.1%) i/s -     19.813M in   5.017089s
String#delete_suffix    4.202M (± 2.1%) i/s -     21.075M in   5.017429s

Comparison:
String#delete_suffix:  4202201.7 i/s
        String#chomp:  3950921.9 i/s - 1.06x  slower
          String#sub:   838415.3 i/s - 5.01x  slower

String#unpack1 vs String#unpack[0] code

Ruby 2.4.0 introduced unpack1 to skip creating the intermediate array object.

$ ruby -v code/string/unpack1-vs-unpack\[0\].rb
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]
Warming up --------------------------------------
      String#unpack1   224.291k i/100ms
    String#unpack[0]   201.870k i/100ms
Calculating -------------------------------------
      String#unpack1      4.864M (± 4.2%) i/s -     24.448M in   5.035203s
    String#unpack[0]      3.778M (± 4.0%) i/s -     18.976M in   5.031253s

Comparison:
      String#unpack1:  4864467.2 i/s
    String#unpack[0]:  3777815.6 i/s - 1.29x  slower

Remove extra spaces (or other contiguous characters) code

The code is tested against contiguous spaces but should work for other chars too.

$ ruby -v code/string/remove-extra-spaces-or-other-chars.rb
ruby 2.5.0p0 (2017-12-25 revision 61468) [x86_64-linux]
Warming up --------------------------------------
 String#gsub/regex+/     1.644k i/100ms
      String#squeeze    24.681k i/100ms
Calculating -------------------------------------
 String#gsub/regex+/     14.668k (± 5.1%) i/s -     73.980k in   5.056887s
      String#squeeze    372.910k (± 8.4%) i/s -      1.851M in   5.011881s

Comparison:
      String#squeeze:   372910.3 i/s
 String#gsub/regex+/:    14668.1 i/s - 25.42x  slower

Time

Time.iso8601 vs Time.parse code

When expecting well-formatted data from e.g. an API, iso8601 is faster and will raise an ArgumentError on malformed input.

$ ruby -v code/time/iso8601-vs-parse.rb
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]
Warming up --------------------------------------
        Time.iso8601    10.234k i/100ms
          Time.parse     4.228k i/100ms
Calculating -------------------------------------
        Time.iso8601    114.485k (± 3.5%) i/s -    573.104k in   5.012008s
          Time.parse     43.711k (± 4.1%) i/s -    219.856k in   5.038349s

Comparison:
        Time.iso8601:   114485.1 i/s
          Time.parse:    43710.9 i/s - 2.62x  slower

Range

cover? vs include? code

cover? only check if it is within the start and end, include? needs to traverse the whole range.

$ ruby -v code/range/cover-vs-include.rb
ruby 2.2.3p173 (2015-08-18 revision 51636) [x86_64-linux]

Calculating -------------------------------------
        range#cover?    85.467k i/100ms
      range#include?     7.720k i/100ms
       range#member?     7.783k i/100ms
       plain compare   102.189k i/100ms
-------------------------------------------------
        range#cover?      1.816M (± 5.6%) i/s -      9.060M
      range#include?     83.344k (± 5.0%) i/s -    416.880k
       range#member?     82.654k (± 5.0%) i/s -    412.499k
       plain compare      2.581M (± 6.2%) i/s -     12.876M

Comparison:
       plain compare:  2581211.8 i/s
        range#cover?:  1816038.5 i/s - 1.42x slower
      range#include?:    83343.9 i/s - 30.97x slower
       range#member?:    82654.1 i/s - 31.23x slower

Less idiomatic but with significant performance ruby

Checkout: https://github.com/fastruby/fast-ruby/wiki/Less-idiomatic-but-with-significant-performance-difference

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