R help - Sep 2012 - S4, polymorphism, and parallelization

I am running Rmpi and MPICH2 to do parallelization in a Windows 7 machine.
I am only using my PC's cores. Parallelization for standard R code works
fine. For S4 code I am having the following problem:

Let us say I have a class A and a subclasses B and C (both B and C
"contains" A). I declared a method

setGeneric(
name = "superClassMethod",
 def = function(object) {standardGeneric("superClassMethod")}
)
setMethod(
f = "superClassMethod",
 signature = "A",
definition = function(object) {
# Some code here
 }
)

At some point I call function paralapply (similar to parLapply) in this way

my.list <- paralapply(some.other.list, superClassMethod, papply_commondata
= envir.vars)

Then I get an error message as follows:

Error message: Error in function (classes, fdef, mtable)  :
  unable to find an inherited method for function "superClassMethod",
for
signature "B"

Error in paralapply(some.other.list, superClassMethod, papply_commondata
envir.vars)

On the other hand, if I redefine the method for classes B and C as follows:

setMethod(
f = "superClassMethod",
signature = "B",
 definition = function(object) {
# Some code here
}
)

setMethod(
f = "superClassMethod",
signature = "C",
 definition = function(object) {
# Some code here
}
)

Obviously this goes against the idea of polymorphism.

How can I solve this problem?

Thanks for any help.

Fernando Saldanha

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