R Under development (unstable) (2024-07-10 r86888 ucrt) -- "Unsuffered Consequences"
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Platform: x86_64-w64-mingw32/x64

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> visualize <- FALSE # TRUE for manual tests with visualization of results
> 
> if(visualize)
+ {
+   
+   library(parallel)
+   
+   
+   #fonction basique evaluant la moyenne empirique d'un echantillon gaussien
+   f <- function(i) mean(rnorm(1e4, mean=i))
+   
+   #exemple simple
+   glist <- 1:20 	
+   cl <- parallel::makeCluster(2)
+   system.time(
+     res <- parallel::parLapply(cl, glist, f)
+   )
+   parallel::stopCluster(cl)
+   
+   
+   #exemple en faisant varier le nombre de coeurs et le nombre de simulations
+   nbsimu <- 10^(1:2)
+   cores <- 1:4
+   cores <- 1:getOption("cl.cores", 2)
+   
+   partime <- matrix(NA, length(nbsimu), length(cores)+1)
+   colnames(partime) <- c("R", paste("core",cores))
+   rownames(partime) <- paste("n", nbsimu, sep="=")
+   
+   partime[, 1] <- sapply(1:length(nbsimu), function(i) 
+     system.time(lapply(1:nbsimu[i], f))[3])
+   for(j in 1:length(cores))
+   {
+     print(cores[j])
+     cl <- parallel::makeCluster(cores[j])
+     partime[, j+1] <- sapply(1:length(nbsimu), function(i) 
+       system.time(parallel::parLapply(cl, 1:nbsimu[i], f))[3])
+     parallel::stopCluster(cl)
+   }		
+   
+   
+   partime
+   
+ }
> 
> proc.time()
   user  system elapsed 
   0.21    0.03    0.23