Simpler seed setting

stan-dev · May 17, 2024 · 1d76ca7 · 1d76ca7
1 parent 5493eb2
commit 1d76ca7
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Showing 2 changed files with 6 additions and 18 deletions.
diff --git a/R/utils.R b/R/utils.R
@@ -889,11 +889,11 @@ prep_fun_cpp <- function(fun_start, fun_end, model_lines) {
   fun_body <- gsub("std::ostream\\*\\s*pstream__\\s*=\\s*nullptr", "", fun_body)
   if (grepl("(stan::rng_t|boost::ecuyer1988)", fun_body)) {
     if (cmdstan_version() < "2.35.0") {
-      fun_body <- gsub("boost::ecuyer1988&\\s*base_rng__", "SEXP base_rng_ptr", fun_body)
+      fun_body <- gsub("boost::ecuyer1988&\\s*base_rng__", "SEXP base_rng_ptr, SEXP seed", fun_body)
     } else {
-      fun_body <- gsub("stan::rng_t&\\s*base_rng__", "SEXP base_rng_ptr", fun_body)
+      fun_body <- gsub("stan::rng_t&\\s*base_rng__", "SEXP base_rng_ptr, SEXP seed", fun_body)
     }
-    rng_seed <- "Rcpp::XPtr<stan::rng_t> base_rng(base_rng_ptr);base_rng->seed(get_seed());"
+    rng_seed <- "Rcpp::XPtr<stan::rng_t> base_rng(base_rng_ptr);base_rng->seed(Rcpp::as<int>(seed));"
     fun_body <- gsub("return", paste(rng_seed, "return"), fun_body)
     fun_body <- gsub("base_rng__,", "*(base_rng.get()),", fun_body, fixed = TRUE)
   }
@@ -957,6 +957,9 @@ compile_functions <- function(env, verbose = FALSE, global = FALSE) {
     fundef <- get(fun, envir = fun_env)
     funargs <- formals(fundef)
     funargs$base_rng_ptr <- env$rng_ptr
+    # To allow for exported RNG functions to respect the R 'set.seed()' call,
+    # we need to derive a seed deterministically from the current RNG state
+    funargs$seed <- quote(sample.int(.Machine$integer.max, 1))
     formals(fundef) <- funargs
     assign(fun, fundef, envir = fun_env)
   }
@@ -1003,9 +1006,3 @@ expose_stan_functions <- function(function_env, global = FALSE, verbose = FALSE)
   }
   invisible(NULL)
 }
-
-# To allow for exported RNG functions to respect the R 'set.seed()' call,
-# we need to derive a seed deterministically from the current RNG state
-get_seed <- function() {
-  sample.int(.Machine$integer.max, 1)
-}
diff --git a/inst/include/stan_rng.hpp b/inst/include/stan_rng.hpp
@@ -15,13 +15,4 @@ namespace stan {
 }
 #endif
 
-// To ensure that exported RNG functions respect changes to R's RNG state,
-// we need to deterministically set the seed of the RNG used by the exported
-// functions.
-int get_seed() {
-  Rcpp::Environment pkg = Rcpp::Environment::namespace_env("cmdstanr");
-  Rcpp::Function f = pkg["get_seed"];
-  return Rcpp::as<int>(f());
-}
-
 #endif