#mclapply function comes from parallel R package
library(parallel)

# Check how many cores are requested by the job
( ncores <- as.numeric( Sys.getenv("NSLOTS") ) )

# If code is executed interactively, set the number of cores manually
if ( is.na(ncores) ) ncores <- 1

# Define a function to be executed by each worker
myFun <- function(x){ sum(x ) }


# Define a sample dataset
set.seed(42)
df <- as.data.frame( 
  matrix(sample(1:100, 100000000, replace=TRUE), nrow=100000) )

# Execute function in parallel using ncores CPU cores
result <- mclapply( df, FUN=myFun, mc.cores = ncores )