Feature #12647
Updated by qitar888 (Chia-sheng Chen) over 8 years ago
I found tanh(x) in math.c return sinh(x) / cosh(x), which function call is a waist of time. So I changed to (exp(2*x) - 1) / (exp(2*x) + 1), the extract form of tanh(). But if HAVE_SINH and HAVE_COSH are defined, only HAVE_TANH undefined (a weird library but possible) Then the origin formulae are faster. Eventually the solution is to determined whether HAVE_SINH/COSH exists, and set the formulae accordingly. Testing Code: ~~~ ruby require 'benchmark/ips' Benchmark.ips do |x| x.config(:times => 1000, :warmup => 5) x.report(RUBY_DESCRIPTION) { Math.tanh(12.345) } end ~~~ Outcome: ~~~ ###### # Origin with HAVE_SINH, HAVE_COSH, HAVE_TANH all undef Warming up -------------------------------------- ruby 2.4.0dev (2016-08-02 trunk 55797) [x86_64-linux] 122.226k i/100ms Calculating ------------------------------------- ruby 2.4.0dev (2016-08-02 trunk 55797) [x86_64-linux] 1.856M (± 4.9%) i/s - 9.289M in 5.016718s ###### # All tag undifined, modified tanh() Warming up -------------------------------------- ruby 2.4.0dev (2016-08-02 trunk 55797) [x86_64-linux] 165.404k i/100ms Calculating ------------------------------------- ruby 2.4.0dev (2016-08-02 trunk 55797) [x86_64-linux] 2.857M (± 2.5%) i/s - 14.390M in 5.039981s ###### # Only HAVE_TANH undifined Warming up -------------------------------------- ruby 2.4.0dev (2016-08-02 trunk 55797) [x86_64-linux] 205.575k i/100ms Calculating ------------------------------------- ruby 2.4.0dev (2016-08-02 trunk 55797) [x86_64-linux] 3.732M (± 2.2%) i/s - 18.707M in 5.015756s ~~~ About 50% improvement when all three tags are undefined. Doesn't drop when only HAVE_TANH is undefined. BTW, I want to ask how to send a patch. Adding a feature here and attaching my patch is enough?