The ruby's Float#to_s
uses David M. Gay's library.
The implementation is based on traditional DRAGON(1)(2), one of the most well known floating point printing algorithm developed by Guy L. Steel, et al.
I recently found another floating point printing library, google/double-conversion, which implements faster algorithm called Grisu(3).
This is an example using the google/double-conversion for Float#to_s
.
- Guy L. Steel, Jr and Jon L. White, How to Print Floating-Point Accurately, PLDI '90, http://dl.acm.org/ft_gateway.cfm?id=93559
- Robert G. Burger and R. Kent Dybvig, Printing Floating-Point Numbers Quickly and Accurately, PLDI '96, http://www.cs.indiana.edu/~dyb/pubs/FP-Printing-PLDI96.pdf
- Florian Loitsch, Printing Floating-Point Numbers Quickly and Accurately with Integers, PLDI '10, http://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf
Grisu version is more than 4 times faster than DRAGON version, Float#to_s
.
$ ruby -I lib test/benchmark.rb
🐉 Small float numbers, count=5000000, range=0.0...1.0
user system total real
Float#to_s 4.500000 0.010000 4.510000 ( 4.527218)
Float#hitokage_to_s 1.070000 0.000000 1.070000 ( 1.083553)
Verifying results...👍
🐉 Usual float numbers, count=5000000, range=0.0...10000000.0
user system total real
Float#to_s 4.650000 0.330000 4.980000 ( 5.004367)
Float#hitokage_to_s 1.210000 0.140000 1.350000 ( 1.364027)
Verifying results...👍
🐉 Big floats numbers, count=5000000, range=1.0e+20...1.0e+30
user system total real
Float#to_s 6.050000 0.240000 6.290000 ( 6.338893)
Float#hitokage_to_s 1.120000 0.000000 1.120000 ( 1.132833)
Verifying results...👍
Add this line to your application's Gemfile:
gem 'hitokage'
And then execute:
$ bundle
Or install it yourself as:
$ gem install hitokage
It defines Float#hitokage_to_s
.
require 'hitokage'
1.0.hitokage_to_s
Or, you can replace the default Float#to_s
.
require 'hitokage/replace_float_to_s'
1.0.to_s
This library generates different string representation than Float#to_s
for some values including 1e-10
and 1e10
.
However, the generated string can be converted to same float number using to_f
.
After checking out the repo, run bin/setup
to install dependencies. Then, run rake test
to run the tests. You can also run bin/console
for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install
. To release a new version, update the version number in version.rb
, and then run bundle exec rake release
, which will create a git tag for the version, push git commits and tags, and push the .gem
file to rubygems.org.
Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/hitokage.
The gem is available as open source under the terms of the MIT License.
The gem contains google/double-conversion.