title: parallel processing with R Package "ranger" in **Windows**
body: <p>I am trying to do parallel processing with R Package "ranger" in <strong>Windows</strong> environment.  I am having no luck.  </p>
  
  <p>In the past, I have done the following to do parallel processing with the R randomForest package with say data "train" and assuming your chip has 8 cores:</p>
  
  <pre><code>library(foreach)
  library(doSNOW)
  library(randomForest)
  registerDoSNOW(makeCluster(8, type="SOCK"))
  system.time( {rf = foreach(ntree = rep(125, 8), .combine = combine, .packages = "randomForest") %dopar% randomForest(y ~ ., data = train, ntree = ntree)} )
  </code></pre>
  
  <p>Basically the code above creates 125 trees in 8 separate cores and then combines the results into one single random forest object by the "combine" command that comes with the randomForest package.</p>
  
  <p>However, the ranger package does not have a combine command and all my attempts to do parallel processing in <strong>Windows</strong> has not work.</p>
  
  <p>The documentation (and the relevant publication) for ranger does not say how to do parallel processing in windows.  </p>
  
  <p>Any ideas how this can be done using ranger and <strong>Windows</strong> environment?</p>
  
  <p>Thank you</p>