R 代码的括号 -> 括号优化是否仍然相关？

Question

前段时间有人讨论过用方括号代替圆括号会如何加速 R 代码。这仍然是正确的，或者对括号的优化已折叠到 R 分布 post 3.1 中？

https://radfordneal.wordpress.com/2010/08/19/speeding-up-parentheses-and-lots-more-in-r/

Answer 1

似乎对我仍然有意义。这并不意味着我会为此失眠。

version
# platform       x86_64-w64-mingw32          
# arch           x86_64                      
# os             mingw32                     
# system         x86_64, mingw32             
# status                                     
# major          3                           
# minor          2.1                         
# year           2015                        
# month          06                          
# day            18                          
# svn rev        68531                       
# language       R                           
# version.string R version 3.2.1 (2015-06-18)
# nickname       World-Famous Astronaut    

a <- 5; b <- 1; c <- 4; d <- NULL
f <- function (n) for (i in 1:n) d <- 1/{a*{b+c}}
system.time(f(10000000))
# user  system elapsed 
# 6.63    0.00    6.64 

a <- 5; b <- 1; c <- 4; d <- NULL
g <- function (n) for (i in 1:n) d <- 1/(a*(b+c))
system.time(g(10000000))
# user  system elapsed 
# 7.27    0.00    7.29

R 代码的括号 -> 括号优化是否仍然相关？

Is the Parenthesis -> Bracket optimization for R code still relevant?

optimization

brackets

r

parentheses