Error: processing vignette failed with diagnostics: 4 simultaneous processes spawned

Question

I am building a vignette for R package mistral (see github.com/clemlaflemme/mistral) and the devtools::check(cleanup = FALSE) returns a Warning

Error: processing vignette 'mistral-vignette.Rmd' failed with diagnostics:
4 simultaneous processes spawned
Execution halted

I could not find any help on Google. Actually I do use parallel computing in the vignette, is it not allowed ?

Stockade

Answer 1

I experienced a similar issue. I got the check to pass if I changed the number of cores from 4 to 2, i.e. in the vignette I set options(mc.cores=2). I couldn't find any clear documentation but I suspect R CMD check only allows a maximum of two cores based on an obscure comment in Hadley Wickham's R Packages Book:

NB: you can’t use unexported functions and you shouldn’t open new graphics devices or use more than two cores. Individual examples shouldn’t take more than 5s.

Chanel

It's not well motivated indeed. Just quoting directly your link : "NB: you can’t use unexported functions and you shouldn’t open new graphics devices or use more than two cores. Individual examples shouldn’t take more than 5s." – Stockade

Answer 2

Checkout this answer to see how you can do this more efficiently:

R CRAN Check fail when using parallel functions

Cohby