update the progress bar only 20 times per second

[mkuhn]

I noticed that RStudio has a high CPU load while running do on data frames with many groups and short operations. I traced this to the fact that the progress bar is re-drawn for each tick, even if it hasn't changed since the last update.

I therefore added a check for when the progress bar has been drawn the last time, and update only if this is more than 50 ms ago. A simple test revealed that this can save a lot of overhead without noticeable changes (first run: normal dplyr, second run: with last_update check):

> d <- data.frame(x=1:100000)
> system.time(invisible(d %>% group_by(x) %>% do(x=0)))
|==========================================================================================|100% ~0 s remaining        
user  system elapsed
 33.535   2.976  28.715 

Restarting R session...

> library(dplyr)
> system.time(invisible(d %>% group_by(x) %>% do(x=0)))
|========================================================================================= | 99% ~0 s remaining
user  system elapsed 
  3.845   0.109   4.009 

[hadley]

Ooops. Thanks for the fix!

Could you please also add a bullet to NEWS?

[mkuhn]

You're welcome! I added a line to NEWS.md.

[mkuhn]

The Travis build failed early on something unrelated:

Downloading GitHub repo hadley/testthat@master
from URL https://api.github.com/repos/hadley/testthat/zipball/master
Error in download(dest, src, auth) : Forbidden (HTTP 403).
Calls: <Anonymous> ... remote_download.github_remote -> download -> <Anonymous>
Execution halted

[hadley]

Awesome - thanks!

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/