The “clusterApply” Function in R

• Package: parallel

• Purpose: Apply a function to each node in a cluster in parallel.

• General class: Parallel computing

• Required argument(s):

• cl: The cluster object created with makeCluster.

• x: A list or vector to be divided among the nodes for processing.

• fun: The function to be applied to each node.

• Notable optional arguments:

• ...: Additional arguments to be passed to the function.

• Example:

• # Load the parallel package
  library(parallel)
  
  # Create a cluster with 4 nodes
  cl <- makeCluster(4)
  
  # Define a function to square a number
  square <- function(x) { return(x^2) }
  
  # Apply the function to each node in the cluster
  result <- clusterApply(cl, 1:10, square)
  
  # Stop the cluster
  stopCluster(cl)
  
  # View the result
  print(result)

• In this example, we create a cluster cl with 4 nodes using the makeCluster function. We define a function square to square a number. Then, we use clusterApply to apply the square function to the numbers 1 to 10 in parallel across the nodes in the cluster. The result is printed to the console.