R using varibales in parLapply

Question

I have a problem with using the variable "Druckfaktor" in parLapply.

My code looks like this:

  Druckfaktor <- 1.3      

  no_cores <- detectCores()-1
  cl <- makeCluster(no_cores)

  S <- parLapply(cl,m.list,function(x) {
        s <- diag(x[2:4])
        s[1,2] <- s[2,1] <- x[5]
        s[2,3] <- s[3,2] <- x[6]
        s[3,1] <- s[1,3] <- x[7]

        VD <- eigen(s)
        V <- VD$vectors
        D <- VD$values
        D[D<0] <- D[D<0]/Druckfaktor
        s <- V %*% diag(D) %*% t(V)
        c(x[1],s[1,1],s[2,2],s[3,3],s[1,2],s[2,3],s[3,1])
  })
  stopCluster(cl)code here

Unfortunately the function answers with:

Error in checkForRemoteErrors(val) : 11 nodes produced errors; first error: Objekt 'Druckfaktor' nicht gefunden

How can I use this "Druckfaktor" together with parLapply?

Thanks

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

1

You have to use clusterExport:

clusterExport(cl = NULL, varlist, envir = .GlobalEnv)

clusterExport assigns the values on the master R process of the variables named in varlist to variables of the same names in the global environment (aka ‘workspace’) of each node. The environment on the master from which variables are exported defaults to the global environment.

In your case:

Druckfaktor <- 1.3      

no_cores <- detectCores()-1
cl <- makeCluster(no_cores)
clusterExport(cl, c("Druckfaktor"))
[...]

edited Jun 20 '20 at 09:12

Community

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answered Jun 06 '18 at 10:21

Ralf Stubner

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Thanks for your answer, unfortunately it doesnt work. Error in get(name, envir = envir) : invalid first argument – Michael Vorndran Jun 06 '18 at 10:36
@Michael, even after fixing the typo `Druckfactor` -> `Druckfaktor`? If so we will need a [mcve]? – Ralf Stubner Jun 06 '18 at 10:40
... solved, I have to hand over the name, i.e. "Druckfaktor" in quotation marks Thanks for your help – Michael Vorndran Jun 06 '18 at 10:44
@Michael, ok fixed in the answer as well. Fell free to accept/up-vote the answer. – Ralf Stubner Jun 06 '18 at 10:52

R using varibales in parLapply

1 Answers1