Parallel computation

[spiry34]

Added optional parallel computation in cartogram_cont.R, relevant for large maps or grids
Added @param documentation line for parallel option
Contributor information added in DESCRIPTION.
New parallel feature added in NEWS.

Parallel computation is slower on small maps (~1-5 hundreds of objects) but really improves computation time on large grids (tested on 4 cores with 3500 objects -> computation time improved by a factor 3.6).

As I use your package for grids anamorphosis, the faster the better ;-)
S.

[sjewo]

Hi @spiry34 ! Thanks for your contribution and pull request!
I'm just back from holidays and quite busy at the moment, but I'll try to take a look into your code in the next days!

[spiry34]

Hello @sjewo,
Don't worry, I'm working on a C++ function for the core process; I'll post another pull-request when finished.
And I'm also going to enjoy 2 weeks of holidays, so ... see you soon!
S.

[spiry34]

Hello @sjewo ,
I found some time to add my new functionalities in cartogram.
Big changes ahead :-)
Note: In order to build the package I used the following commands:

usethis::use_rcpp()
pkgbuild::check_build_tools(debug = TRUE)
devtools::document()
devtools::build()

If you find some weird stuff, I'll do my best to explain or correct.
Enjoy!
All the best,
S.

[sjewo]

Hey @spiry34,

thanks for the update!

I'll start to add some tests for the current implementation, so I can test your code thoroughly :)

[richardneilbelcher]

Just to say that using this update seems to shorten the run time for each iteration when using one core. However, I am getting the following error when I try I set parallel = TRUE

Error in data.frame(id = 1:length(x.sp@polygons)) :object 'x.sp' not found

I have tried using both sf and SpatialPolygonsDataFrame objects. It looks like x.sp isnt defined until line 252 but the data.frame is being made on line 192