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Feature #16851

Ruby hashing algorithm could be improved using Tabulation Hashing

Added by ana06 (Ana Maria Martinez Gomez) 3 months ago. Updated 3 months ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:98292]

Description

I have implemented Linear Probing and Simple tabulation in Ruby: https://github.com/Ana06/ruby/compare/master...Ana06:tabulation

I tested it using the following code:
https://github.com/Ana06/ruby-tabulation/blob/master/benchmark_tabulation.rb
It benchmarks the insertion of 600000 elements (by hashing their 64 bits ids) in an empty hash 100 times. Below are the times (in seconds) I got executing this code for different versions of the Ruby code:

  • master (without Simple Tabulation): 29.68
  • master with Linear Probing (without Simple Tabulation): 99.76
  • master with Quadratic Probing (without Simple Tabulation): 29.97
  • master with Simple Tabulation: 15.76
  • master with Linear Probing and Simple Tabulation: 24.23
  • master with Quadratic Probing and Simple Tabulation: 13.73

master refers to ruby 2.8.0dev:
(2020-05-07T16:22:38Z master 7ded8fd) [x86_64-linux].
I tried with 8 x Intel i5-8265U.

Although this is just a proof of concept and not something that could be already use in production, I think it proves the potential of Simple Tabulation to improve current Ruby implementation. It may be worthwhile to explore this idea further. What do you think?

I did this as part of a project for my Advanced Algorithms course. For more details check the project report:
https://github.com/Ana06/ruby-tabulation/blob/master/latex/RubyTabulation_Project.pdf

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