For the record: I filed a bug report here
https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17807 and this is a more polished minimal example library(parallel) nslaves <- 2 cl <- makeCluster(nslaves) X <- matrix(c(1,0,1),1,3) res <- parCapply(cl,X,FUN=function(x){ y <- x[1] if(y==1){ out <- y }else{ out <- double(0) } return(out) }) > res [[1]] [1] 1 [[2]] numeric(0) [[3]] [1] 1 Simone On Mon, May 18, 2020 at 5:23 PM Simone Giannerini <sgianner...@gmail.com> wrote: > > According to ?parCapply: > > parRapply and parCapply always return a vector. > > This appears not to be the case in the following minimal reproducible example: > > > library(parallel) > > nslaves <- 2 > > cl <- makeCluster(nslaves) > > X <- matrix(2,nrow=3,ncol=4) > > X <- rbind(c(1,1,0,1),X) > > tv <- parCapply(cl,X,FUN=function(x){ > + ind <- x[1] > + y <- x[-1] > + if(ind==1){ > + r1 <- sum(y) > + }else{ > + r1 <- logical(0) > + } > + return(unlist(as.numeric(c(ind,r1)))) > + }) > > tv > [[1]] > [1] 1 > > [[2]] > [1] 6 > > [[3]] > [1] 1 > > [[4]] > [1] 6 > > [[5]] > [1] 0 > > [[6]] > [1] 1 6 > > > class(tv) > [1] "list" > > sessionInfo() > R version 4.0.0 (2020-04-24) > Platform: x86_64-w64-mingw32/x64 (64-bit) > Running under: Windows 10 x64 (build 18363) > > Matrix products: default > > locale: > [1] LC_COLLATE=Italian_Italy.1252 LC_CTYPE=Italian_Italy.1252 > [3] LC_MONETARY=Italian_Italy.1252 LC_NUMERIC=C > [5] LC_TIME=Italian_Italy.1252 > > attached base packages: > [1] parallel stats graphics grDevices utils datasets > methods base > > loaded via a namespace (and not attached): > [1] compiler_4.0.0 > > -- > _________________________________________________________________ > > PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A > Theme issue ‘DNA as information’ > edited by Julyan H.E. Cartwright, Simone Giannerini and Diego L. González > _________________________________________________________________ > > Simone Giannerini > Dipartimento di Scienze Statistiche "Paolo Fortunati" > Universita' di Bologna > Via delle belle arti 41 - 40126 Bologna, ITALY > Tel: +39 051 2098262 Fax: +39 051 232153 > https://www.unibo.it/sitoweb/simone.giannerini/ > ______________________________________________________ -- ___________________________________________________ Simone Giannerini Dipartimento di Scienze Statistiche "Paolo Fortunati" Universita' di Bologna Via delle belle arti 41 - 40126 Bologna, ITALY Tel: +39 051 2098262 Fax: +39 051 232153 https://simonegiannerini.net/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
