CODEWITHSUNDEEP
pythonrparallel-processingshinydoparallel
jacob mathew
jacob mathew

Reputation: 153

Parallel processing in R shiny, calling Python script

I am trying to do parallel processing in R shiny, the parallel task which I want to do is a call to python script. However it does not work and not able to fetch the result back from python to R. Below is the sample R shiny and Python code. App.R

library(shiny)
library(reticulate)
library(doParallel)
library(foreach)
ui <- fluidPage(

   # Application title
   titlePanel("Sample Program"),

      mainPanel(
         uiOutput("txtValue")
      )   
)
server <- function(input, output) {

  source_python("../../PythonCode/Multiprocessing/multip.py")  

  cl <- makeCluster(detectCores(), type='PSOCK')
  registerDoParallel(cl)

  result <- foreach(i=1:5) %dopar% fsq(i)
  stopCluster(cl)     
   output$txtValue <- renderUI({
    result   
   }) 

}
shinyApp(ui = ui, server = server)

Python Code (multip.py)

def fsq(x):
    return x**2

Upvotes: 2

Views: 1821

Answers (1)

Ralf Stubner
Ralf Stubner

Reputation: 26823

The error message is independent of shiny:

library(reticulate)
library(doParallel)
library(foreach)
library(parallel)

source_python("multip.py")  

cl <- makeCluster(detectCores(), type = 'PSOCK')
registerDoParallel(cl)

# throws: Error in unserialize(socklist[[n]]) : error reading from connection
foreach(i = 1:5) %dopar% fsq(i)

stopCluster(cl)

I interpret this such that one cannot serialize a Python function as one can serialize a R function. A simple workaround is to use source_python within the loop:

library(doParallel)
library(foreach)
library(parallel)

cl <- makeCluster(detectCores(), type = 'PSOCK')
registerDoParallel(cl)

foreach(i = 1:5) %dopar% {
  reticulate::source_python("multip.py")  
  fsq(i)
}
stopCluster(cl)

Upvotes: 3

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