[R-sig-Geo] clusterR: error when using a cluster object passed as an argument to function

[Guillaume Drolet]

Hi,

I have a function, say fun1, in which I create a SNOW cluster object using:

beginCluster(nodes)   
cl <- getCluster()

Then I export variables to the cores (nodes) and load some libraries:

clusterExport(cl, c("tmpdir", "maxmemory", "chunksize"))
clusterEvalQ(cl, c(library(raster), library(rgdal),  rasterOptions(tmpdir = 
        tmpdir, maxmemory = maxmemory, chunksize = chunksize)))

Later in my function, I call a bunch of other functions to which I pass cl
as one of their arguments.
For exemple, say I have fun2 to which I pass cl which in turn is used in a
call to clusterR:

fun2 <- function(x, b, prl, cl) {
  
  if (prl & !inMemory(x)) {    
    f1 <- function(x, y) {     
      min(x != y - 1)      
    }
    
    nm <- clusterR(x, fun = f1, args = list(b), cl = cl)    
  } else {
    nm <- min(x != b - 1)
  }

   return(nm)
}
When I run fun1 and it gets to the first function which uses cl (fun2 in
this example), this results in the error:

Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘writeStart’ for signature
‘"RasterLayer", "SOCKcluster"’

At the moment I don't have a clue about the source of the problem. Only
thing I know is that it used to work when I was running fun1 line by line
and not by calling the function. Thanks for your help!



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