Fit same model on many datasets with purrr::map

Interfaces RStan
1

I have just started using RStan to work on some fairly simple dynamic factor models. I have data on a bunch of countries and would like to fit the same DFM on each country separately in a tidy way.
For this I arranged time series data in a nested dataframe - where countries are nesting variables and data are collapsed in a column of lists. Then I wanted to use purrr::map to apply the same model to every element of the column of lists, ie the data for a single country, with a custom function

## custom function
stan_map <- function(.data, .stan_mdl, ..., fct_vars=keep_vars){
  
  # remove NAs and cols
  clean_x <- .data %>% 
    select(
      date,
      all_of(fct_vars)
    ) %>% 
    na.omit()
  
  # shape into list
  mod_list <- list(
    T = nrow(clean_x),
    N = ncol(clean_x) - 2,
    Y = clean_x[, c(-1, -2)]
  )
  
  # run stan model
  stanout <- sampling(
    object = .stan_mdl,
    data = mod_list,
    refresh = -1,
    open_progress = F,
   # extra options
    ...
  )  
  return(stanout)
}

Then I use mutate and map to just add another column of lists where each element should be the output of the sampling, like this

# compile stan model from file 
bdfm2 <- stan_model(
  file = "./f2.stan",
  model_name = "BDFM2",
  verbose = T,
  auto_write = T
)

# apply to individual countries
data_nest <- data_nest %>% 
  mutate(
    stan_obj = map(
      .f = stan_map, 
      .x = ctry_data, 
      .stan_mdl = bdfm2,
      # for testing
      iter = 1000,
      chains = 1,
      cores = 1
    )
  )

Now, for some reason R crashes without any error message or warning and I am left without any clues on how to correctly fit models in a tidy way with map. My hunch is that it has something to do with parallelization and some clashes between purrr:map and rstan, also because the custom function alone works outside the mutate+map. I am running on Win10 with R 4.2.1 and RStan 2.26.23; I cannot use cmdstan since I am on a restricted corp machine.

2

@bgoodri should know the answer to this one.

3

Thanks! in the meantime I found out a way to make it work: I switched from map to map2 and it seems to work!
Still, it is not clear to me how the simplest map implementation does not work properly…