Comparing array subset checks

README.md

@@ -389,6 +389,32 @@ Comparison:
         Array#insert:        0.2 i/s - 262.56x slower
 ```
 
+##### Subset detection with various methods [code](code/array/subset-checking.rb)
+
+```
+$ ruby -v code/array/subset-checking.rb
+ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux]
+Warming up --------------------------------------
+    (a1 - a2).empty?    19.534k i/100ms
+     (a1 & a2) == a1    16.190k i/100ms
+ Array#all?#include?    27.391k i/100ms
+        Array#&#size    16.949k i/100ms
+         Set#subset?     4.289k i/100ms
+Calculating -------------------------------------
+    (a1 - a2).empty?    206.885k (± 2.0%) i/s -      1.035M in   5.006270s
+     (a1 & a2) == a1    169.425k (± 2.4%) i/s -    858.070k in   5.067497s
+ Array#all?#include?    291.863k (± 2.1%) i/s -      1.479M in   5.070021s
+        Array#&#size    176.342k (± 2.9%) i/s -    898.297k in   5.098513s
+         Set#subset?     43.342k (± 3.0%) i/s -    218.739k in   5.051749s
+
+Comparison:
+ Array#all?#include?:   291862.7 i/s
+    (a1 - a2).empty?:   206885.5 i/s - 1.41x  slower
+        Array#&#size:   176341.9 i/s - 1.66x  slower
+     (a1 & a2) == a1:   169424.9 i/s - 1.72x  slower
+         Set#subset?:    43341.6 i/s - 6.73x  slower
+```
+
 ### Enumerable
 
 ##### `Enumerable#each + push` vs `Enumerable#map` [code](code/enumerable/each-push-vs-map.rb)

code/array/subset-checking.rb

@@ -0,0 +1,34 @@
+require 'benchmark/ips'
+require 'set'
+
+ARRAY1 = [*1..25]
+ARRAY2 = [*1..100]
+
+def slow_set
+  ARRAY2.to_set.subset?(ARRAY1.to_set)
+end
+
+def slow_interception
+  (ARRAY1 & ARRAY2) == ARRAY1
+end
+
+def slow_interception_size
+  (ARRAY1 & ARRAY2).size == ARRAY1.size
+end
+
+def slow_minus_empty
+  (ARRAY1 - ARRAY2).empty?
+end
+
+def fast
+  ARRAY1.all?{|element| ARRAY2.include?(element) }
+end
+
+Benchmark.ips do |x|
+  x.report("(a1 - a2).empty?") { slow_minus_empty }
+  x.report("(a1 & a2) == a1") { slow_interception }
+  x.report("Array#all?#include?") { fast }
+  x.report("Array#&#size") { slow_interception_size }
+  x.report("Set#subset?") { slow_set }
+  x.compare!
+end