Hey,

I have written a simple function Rcpp package, the function is the following:

#include <Rcpp.h>
using namespace Rcpp;
//[[Rcpp::export]]
SEXP Test(double &i){
    double j=std::pow(i,2.0);
    return Rcpp::wrap(j);
}

I can source the code and run the function Test.

But I want to do it in parallel using the BiocParallel::bplapply function like:

snow <- BiocParallel::SnowParam(workers = 4, type = 'SOCK', progressbar=FALSE)
BiocParallel::register(snow, default=TRUE)

BiocParallel::bplapply(X = as.list(seq_len(1000)), FUN=Test)

Then I get the following error:

Error: BiocParallel errors
  element index: 1, 2, 3, 4, 5, 6, ...
  first error: NULL value passed as symbol address

If on the other hand I register only one core (workers=1) the function runs successfully.

What may be causing the problem?

Thank you!

'Snow' params are separate processes, so any memory allocated in the main thread is unknown to the worker thread. You need to source the code on the worker 

bplapply(as.list(seq_len(1000), FUN = function(i) {
    source("your.cpp")
    Test(i)
})

if sourcing the your cpp file is costly, then follow the Rcpp recommendations and create a package; loading the package will be a 'no-op' except for the first time

bplapply(as.list(seq_len(1000), FUN = function(i) {
    library("YourLIbrary")
    Test(i)
})