Merge pull request #1173 from RcppCore/bugfix/remove_rngscope_from_examples

update old examples with respect to RNGScope (closes #1172)

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,11 @@
+2021-09-05  Dirk Eddelbuettel  <[email protected]>
+
+	* inst/examples/Misc/piSugar.cpp (piSugar): Remove spurious call to
+	RNGScope we do not need with Rcpp Attributes
+	* inst/examples/RcppGibbs/RcppGibbs.R (Rgibbs): Comment on two uses
+	of RNGScope as historical in pre-Attributes code
+	* inst/examples/RcppGibbs/timeRNGs.R: Idem for one more
+
 2021-08-05  Dirk Eddelbuettel  <[email protected]>
 
 	* inst/bib/Rcpp.bib: Use https for CRAN URLs

inst/examples/Misc/piSugar.cpp

@@ -5,9 +5,8 @@ using namespace Rcpp;
 
 // [[Rcpp::export]]
 double piSugar(const int N) {
-  RNGScope scope;		// ensure RNG gets set/reset
-  NumericVector x = runif(N);
-  NumericVector y = runif(N);
-  NumericVector d = sqrt(x*x + y*y);
-  return 4.0 * sum(d < 1.0) / N;
+    NumericVector x = runif(N);
+    NumericVector y = runif(N);
+    NumericVector d = sqrt(x*x + y*y);
+    return 4.0 * sum(d < 1.0) / N;
 }

inst/examples/RcppGibbs/RcppGibbs.R

@@ -100,7 +100,7 @@ gibbscode <- '
   int i,j;
   NumericMatrix mat(N, 2);
 
-  RNGScope scope;         // Initialize Random number generator
+  RNGScope scope;         // Initialize Random number generator. Not needed when Attributes used.
 
   // The rest of the code follows the R version
   double x=0, y=0;
@@ -174,10 +174,10 @@ NumericMatrix RcppGibbs(int N, int thn){
 
     // Setup storage matrix
     NumericMatrix mat(N, 2);
-    
+
     // The rest of the code follows the R version
     double x = 0, y = 0;
-    
+
     for (int i = 0; i < N; i++) {
         for (int j = 0; j < thn; j++) {
             x = R::rgamma(3.0,1.0/(y*y+4));
@@ -186,14 +186,14 @@ NumericMatrix RcppGibbs(int N, int thn){
         mat(i,0) = x;
         mat(i,1) = y;
     }
-    
+
     return mat;             // Return to R
 }')
 
 
 ## Use of the sourceCpp() is preferred for users who wish to source external
 ## files or specify their headers and Rcpp attributes within their code.
-## Code here is able to easily be extracted and placed into its own C++ file. 
+## Code here is able to easily be extracted and placed into its own C++ file.
 
 ## Compile and Load
 sourceCpp(code="
@@ -219,7 +219,7 @@ NumericMatrix GSLGibbs(int N, int thin){
         mat(i,1) = y;
     }
     gsl_rng_free(r);
-    
+
     return mat;           // Return to R
 }")
 
@@ -289,5 +289,3 @@ print(res)
 
 
 ## And we are done
-
-

inst/examples/RcppGibbs/timeRNGs.R

@@ -3,111 +3,36 @@ suppressMessages(library(Rcpp))
 suppressMessages(library(inline))
 suppressMessages(library(rbenchmark))
 
-## NOTE: This is the old way to compile Rcpp code inline.
-## The code here has left as a historical artifact and tribute to the old way.
-## Please use the code under the "new" inline compilation section.
-
-rcppGamma_old <- cxxfunction(signature(xs="numeric"), plugin="Rcpp", body='
-  NumericVector x(xs);
-  int n   = x.size();
-
-  // Initialize Random number generator
-  RNGScope scope;
-
-  const double y = 1.234;
-  for (int i=0; i<n; i++) {
-    x[i] = ::Rf_rgamma(3.0, 1.0/(y*y+4));
-  }
-
-  // Return to R
-  return x;
-')
-
-
-gslGamma_old <- cxxfunction(signature(xs="numeric"), plugin="RcppGSL",
-                        include='#include <gsl/gsl_rng.h>
-                                 #include <gsl/gsl_randist.h>',
-                        body='
-  NumericVector x(xs);
-  int n   = x.size();
-
-  gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
-  const double y = 1.234;
-  for (int i=0; i<n; i++) {
-    x[i] = gsl_ran_gamma(r,3.0,1.0/(y*y+4));
-  }
-  gsl_rng_free(r);
-
-  // Return to R
-  return x;
-')
-
-
-rcppNormal_old <- cxxfunction(signature(xs="numeric"), plugin="Rcpp", body='
-  NumericVector x(xs);
-  int n   = x.size();
-
-  // Initialize Random number generator
-  RNGScope scope;
-
-  const double y = 1.234;
-  for (int i=0; i<n; i++) {
-    x[i] = ::Rf_rnorm(1.0/(y+1),1.0/sqrt(2*y+2));
-  }
-
-  // Return to R
-  return x;
-')
-
-
-gslNormal_old <- cxxfunction(signature(xs="numeric"), plugin="RcppGSL",
-                        include='#include <gsl/gsl_rng.h>
-                                 #include <gsl/gsl_randist.h>',
-                        body='
-  NumericVector x(xs);
-  int n   = x.size();
-
-  gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
-  const double y = 1.234;
-  for (int i=0; i<n; i++) {
-    x[i] = 1.0/(y+1)+gsl_ran_gaussian(r,1.0/sqrt(2*y+2));
-  }
-  gsl_rng_free(r);
-
-  // Return to R
-  return x;
-')
-
-
 ## NOTE: Within this section, the new way to compile Rcpp code inline has been
-## written. Please use the code next as a template for your own project.
+## written. Please use the code next as a template for your own project, and
+## do NOT use the old code below
 
 cppFunction('
 NumericVector rcppGamma(NumericVector x){
     int n   = x.size();
-    
+
     const double y = 1.234;
     for (int i=0; i<n; i++) {
         x[i] = R::rgamma(3.0, 1.0/(y*y+4));
     }
-    
+
     // Return to R
     return x;
 }')
 
-## This approach is a bit sloppy. Generally, you will want to use 
+## This approach is a bit sloppy. Generally, you will want to use
 ## sourceCpp() if there are additional includes that are required.
 cppFunction('
 NumericVector gslGamma(NumericVector x){
     int n   = x.size();
-    
+
     gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
     const double y = 1.234;
     for (int i=0; i<n; i++) {
         x[i] = gsl_ran_gamma(r,3.0,1.0/(y*y+4));
     }
     gsl_rng_free(r);
-    
+
     // Return to R
     return x;
 }', includes = '#include <gsl/gsl_rng.h>
@@ -118,18 +43,18 @@ NumericVector gslGamma(NumericVector x){
 cppFunction('
 NumericVector rcppNormal(NumericVector x){
     int n   = x.size();
-    
+
     const double y = 1.234;
     for (int i=0; i<n; i++) {
         x[i] = R::rnorm(1.0/(y+1),1.0/sqrt(2*y+2));
     }
-    
+
     // Return to R
     return x;
 }')
 
 
-## Here we demonstrate the use of sourceCpp() to show the continuity 
+## Here we demonstrate the use of sourceCpp() to show the continuity
 ## of the code artifact.
 
 sourceCpp(code = '
@@ -144,14 +69,14 @@ using namespace Rcpp;
 // [[Rcpp::export]]
 NumericVector gslNormal(NumericVector x){
     int n   = x.size();
-    
+
     gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
     const double y = 1.234;
     for (int i=0; i<n; i++) {
         x[i] = 1.0/(y+1)+gsl_ran_gaussian(r,1.0/sqrt(2*y+2));
     }
     gsl_rng_free(r);
-    
+
     // Return to R
     return x;
 }')
@@ -167,3 +92,85 @@ res <- benchmark(rcppGamma(x),
 print(res)
 
 
+
+
+
+##
+##
+##  Old code below. Do not use in new projects, it is here solely for comparison
+##
+##
+
+
+## NOTE: This is the old way to compile Rcpp code inline.
+## The code here has left as a historical artifact and tribute to the old way.
+## Please use the code under the "new" inline compilation section.
+
+rcppGamma_old <- cxxfunction(signature(xs="numeric"), plugin="Rcpp", body='
+  NumericVector x(xs);
+  int n   = x.size();
+
+  RNGScope scope;         // Initialize Random number generator. Not needed when Attributes used.
+
+  const double y = 1.234;
+  for (int i=0; i<n; i++) {
+    x[i] = ::Rf_rgamma(3.0, 1.0/(y*y+4));
+  }
+
+  // Return to R
+  return x;
+')
+
+
+gslGamma_old <- cxxfunction(signature(xs="numeric"), plugin="RcppGSL",
+                        include='#include <gsl/gsl_rng.h>
+                                 #include <gsl/gsl_randist.h>',
+                        body='
+  NumericVector x(xs);
+  int n   = x.size();
+
+  gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
+  const double y = 1.234;
+  for (int i=0; i<n; i++) {
+    x[i] = gsl_ran_gamma(r,3.0,1.0/(y*y+4));
+  }
+  gsl_rng_free(r);
+
+  // Return to R
+  return x;
+')
+
+
+rcppNormal_old <- cxxfunction(signature(xs="numeric"), plugin="Rcpp", body='
+  NumericVector x(xs);
+  int n   = x.size();
+
+  RNGScope scope;         // Initialize Random number generator. Not needed when Attributes used.
+
+  const double y = 1.234;
+  for (int i=0; i<n; i++) {
+    x[i] = ::Rf_rnorm(1.0/(y+1),1.0/sqrt(2*y+2));
+  }
+
+  // Return to R
+  return x;
+')
+
+
+gslNormal_old <- cxxfunction(signature(xs="numeric"), plugin="RcppGSL",
+                        include='#include <gsl/gsl_rng.h>
+                                 #include <gsl/gsl_randist.h>',
+                        body='
+  NumericVector x(xs);
+  int n   = x.size();
+
+  gsl_rng *r = gsl_rng_alloc(gsl_rng_mt19937);
+  const double y = 1.234;
+  for (int i=0; i<n; i++) {
+    x[i] = 1.0/(y+1)+gsl_ran_gaussian(r,1.0/sqrt(2*y+2));
+  }
+  gsl_rng_free(r);
+
+  // Return to R
+  return x;
+')