Write Stan code to a file — write_stan

Convenience function for writing Stan code to a (possibly temporary) file with a .stan extension. By default, the file name is chosen deterministically based on a hash of the Stan code, and the file is not overwritten if it already has correct contents. This means that calling this function multiple times with the same Stan code will reuse the compiled model. This also however means that the function is potentially not thread-safe. Using hash_salt = Sys.getpid() should ensure thread-safety in the rare cases when it is needed.

write_stan_file(
  code,
  dir = getOption("cmdstanr_write_stan_file_dir", tempdir()),
  basename = NULL,
  force_overwrite = FALSE,
  hash_salt = ""
)

Arguments

code: (character vector) The Stan code to write to the file. This can be a character vector of length one (a string) containing the entire Stan program or a character vector with each element containing one line of the Stan program.
dir: (string) An optional path to the directory where the file will be written. If omitted, a global option cmdstanr_write_stan_file_dir is used. If the global options is not set, temporary directory is used.
basename: (string) If dir is specified, optionally the basename to use for the file created. If not specified a file name is generated from hashing the code.
force_overwrite: (logical) If set to TRUE the file will always be overwritten and thus the resulting model will always be recompiled.
hash_salt: (string) Text to add to the model code prior to hashing to determine the file name if basename is not set.

Value

The path to the file.

Examples

# stan program as a single string
stan_program <- "
data {
  int<lower=0> N;
  array[N] int<lower=0,upper=1> y;
}
parameters {
  real<lower=0,upper=1> theta;
}
model {
  y ~ bernoulli(theta);
}
"

f <- write_stan_file(stan_program)
print(f)
#> [1] "/var/folders/s0/zfzm55px2nd2v__zlw5xfj2h0000gn/T/RtmpWzIPg0/model_7f12fc190dd23b0e462f7d73040dd97e.stan"

lines <- readLines(f)
print(lines)
#>  [1] ""                                   "data {"                            
#>  [3] "  int<lower=0> N;"                  "  array[N] int<lower=0,upper=1> y;"
#>  [5] "}"                                  "parameters {"                      
#>  [7] "  real<lower=0,upper=1> theta;"     "}"                                 
#>  [9] "model {"                            "  y ~ bernoulli(theta);"           
#> [11] "}"                                  ""                                  
cat(lines, sep = "\n")
#> 
#> data {
#>   int<lower=0> N;
#>   array[N] int<lower=0,upper=1> y;
#> }
#> parameters {
#>   real<lower=0,upper=1> theta;
#> }
#> model {
#>   y ~ bernoulli(theta);
#> }
#> 

# stan program as character vector of lines
f2 <- write_stan_file(lines)
identical(readLines(f), readLines(f2))
#> [1] TRUE