duping an Identity Hash/Set is faster than creating a new one #230

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1. JuanVqz commented on Mar 7, 2025

   

   JuanVqz

   on Mar 7, 2025

   Member

   More actions

   @amomchilov could you please opne a PR?
2. BigwWinner commented on Aug 12, 2026

   

   BigwWinner

   on Aug 12, 2026

   More actions

   It's one less allocation, too :)

   YJIT off YJIT on
   Set.new.compare_by_identity 2.571M 4.260M
   S.dup 3.014M 4.999M
   ∆ 1.17x 1.17x
   YJIT off YJIT on
   Hash.new.compare_by_identity 5.643M 8.208M
   H.dup 5.988M 9.014M
   ∆ 1.06x 1.09x
   S = Set.new.compare_by_identity.freeze
   H = Hash.new.compare_by_identity.freeze

   Benchmark.ips do |x|
   x.config(time: 10)

   x.report(".new.compare_by_identity") do |times|
   i = 0
   while (i += 1) <= times
   S.dup
   end
   end

   x.report(".dup ") do |times|
   i = 0
   while (i += 1) <= times
   Set.new.compare_by_identity
   end
   end

   x.compare!
   end

   Benchmark.ips do |x|
   x.config(time: 10)

   x.report(".new.compare_by_identity") do |times|
   i = 0
   while (i += 1) <= times
   H.dup
   end
   end

   x.report(".dup ") do |times|
   i = 0
   while (i += 1) <= times
   Hash.new.compare_by_identity
   end
   end

   x.compare!
   end