Differentiate model and function rng

Author: andrjohns

R/utils.R

@@ -760,7 +760,9 @@ expose_model_methods <- function(env, verbose = FALSE, hessian = FALSE) {
 }
 
 initialize_model_pointer <- function(env, datafile_path, seed = 0) {
-  env$model_ptr_ <- env$model_ptr(ifelse(is.null(datafile_path), "", datafile_path), seed)
+  ptr_and_rng <- env$model_ptr(ifelse(is.null(datafile_path), "", datafile_path), seed)
+  env$model_ptr_ <- ptr_and_rng$model_ptr
+  env$model_rng_ <- ptr_and_rng$base_rng
   env$num_upars_ <- env$get_num_upars(env$model_ptr_)
   env$param_metadata_ <- env$get_param_metadata(env$model_ptr_)
   invisible(NULL)

inst/include/model_methods.cpp

@@ -1,6 +1,7 @@
 #include <Rcpp.h>
 #include <stan/model/log_prob_grad.hpp>
 #include <stan/model/log_prob_propto.hpp>
+#include <boost/random/additive_combine.hpp>
 #ifdef CMDSTAN_JSON
 #include <cmdstan/io/json/json_data.hpp>
 #else
@@ -25,12 +26,15 @@ using json_data_t = stan::json::json_data;
 }
 
 // [[Rcpp::export]]
-SEXP model_ptr(std::string data_path, boost::uint32_t seed) {
+Rcpp::List model_ptr(std::string data_path, boost::uint32_t seed) {
   Rcpp::XPtr<stan_model> ptr(
-    new stan_model(*var_context(data_path), seed, &Rcpp::Rcout),
-    true
+    new stan_model(*var_context(data_path), seed, &Rcpp::Rcout)
+  );
+  Rcpp::XPtr<boost::ecuyer1988> base_rng(new boost::ecuyer1988(seed));
+  return Rcpp::List::create(
+    Rcpp::Named("model_ptr") = ptr,
+    Rcpp::Named("base_rng") = base_rng
   );
-  return ptr;
 }
 
 // [[Rcpp::export]]