How to pass to .f, character vectors in .x that reference global values?

[delt87]

Cross posting this on here since on SO this question is not getting much traction. What is the appropriate way to pass to .f a list of character vectors in .x that reference global Values so that future_map in multisession can locate the global objects referenced?

The reason I'm assigning the df values to my global environment is to try and lower the size of the globals exported as this is significantly slowing the code when running multisession on remote clusters. In reality, my df list containing variable values is a large file that kills any benefits of running multisession on remote clusters.

Consider the following reproducible example:

library(future)
library(furrr)
library(kit)
library(tictoc)
library(tidyverse)

options(future.rng.onMisuse = "ignore")

plan(multisession)

## reprex data
vars <- paste0(letters,1:10)
bestVars <- combn(vars, 5, simplify = F)
df <- data.frame(
  matrix(data = rnorm(50000*length(vars),200,500), nrow = 50000, ncol = length(vars))
)
names(df) <- vars
df$actual_value <- rnorm(n = nrow(df), 350, 300)
df <- df %>%
  dplyr::select(actual_value,everything(.))
df <- lapply(split.default(x = df, names(df)), function(x) x[[1]])

list2env(df, globalenv())

rm(df)

## function to run variables combination in paralell in local machine
run_sim_in_par <- function(vars_to_sim)
{
  sampled_rows <- sample(x = length(actual_value), size = 50, replace = F)
  varname <- paste(names(vars_to_sim), collapse = "*")
  best <- Reduce(vars_to_sim, f = '*')[sampled_rows]
  row_idx <- kit::topn(best, n = 5, decreasing = T, hasna = FALSE, index = TRUE)
  
  best_row_actual_value <- actual_value[sampled_rows][row_idx]
  
  sim <- data.frame(var = varname,
                    mean_actual_value = mean(best_row_actual_value))
  return(sim)
}

## testing to ensure run_sim_par function works
x <- bestVars[[1]]
simulated_res <- run_sim_in_par(vars_to_sim = mget(x))

> simulated_res
var                   mean_actual_value
1 a1*b2*c3*d4*e5            361.17

## attempt to pass .x to custom function (doesn't know where to find .x values)
future_map(
  .x = bestVars,
  .f = ~run_sim_in_par(vars_to_sim = mget(.x))
)

Error in (function (.x, .f, ..., .progress = FALSE)  : 
  ℹ In index: 1.
Caused by error:
! value for 'a1' not found

## what if i expclicitly declare the .x values in furr_options(globals....); test just one list element first?
future_map(
  .x = bestVars[[1]],
  .f = ~run_sim_in_par(vars_to_sim = mget(.x)),
  .options = furrr_options(globals = c(bestVars[[1]], "run_sim_in_par", "actual_value"))
)

Error in future$envir$...future.seeds_ii : 
  $ operator is invalid for atomic vectors