clusterExport, environment and variable scoping

You’re getting the error when calling clusterExport(cl, list("a", "b", "data")) because clusterExport is trying to find the variables in .GlobalEnv, but fn1 isn’t setting them in .GlobalEnv but in its own local environment.

An alternative is to pass the local environment of fn1 to fn2, and specify that environment to clusterExport. The call to fn2 would be:

c <- fn2(m, environment())

If the arguments to fn2 are function(x, env), then the call to clusterExport would be:

clusterExport(cl, list("a", "b", "data"), envir = env)

Since environments are passed by reference, there should be no performance problem doing this.