parcumsum <- function(cls,x) {
   nWorkers <- length(cls)
   chunkRanges <- splitIndices(length(x),nWorkers)
   clusterApply(cls,chunkRanges,
      function(oneRange) myx <<- x[oneRange])
   tmp <- clusterEvalQ(cls,cumsum(myx))
   endValue <- function(x) x[length(x)]
   evs <- sapply(tmp,endValue)
   base <- evs[1]
   for (i in 2:nWorkers) {
      tmp[[i]] <- tmp[[i]] + base
      base <- base + evs[i]
   }
   Reduce(c,tmp)
}     

test <- function() {
   library(parallel)
   cls <- makeCluster(2)
   x <- sample(1:5,10,replace=TRUE)
   print(x)
   print(parcumsum(cls,x))
}

test()