[R] Adding comment in C++ code for debugging purpose

[Rui Barradas]

Às 13:38 de 17/12/2022, Christofer Bogaso escreveu:
> Hi,
> 
> Below is the position of Rcout and underlying C++ function
> 
> #ifdef _OPENMP
> #include <omp.h>
> #endif
> // [[Rcpp::depends(RcppProgress)]]
> #include <progress.hpp>
> #include "cpploss.h"
> #include <Rcpp.h>
> #include <Rmath.h>
> #include <iostream>
> 
> using namespace Rcpp;
> 
> // [[Rcpp::export]]
> SEXP  GCPM_cpploss(SEXP default_distr_a,SEXP link_function_a, SEXP
> S_a,SEXP Sigma_a, SEXP W_a, SEXP PD_a, SEXP PL_a, SEXP calc_rc_a, SEXP
> loss_thr_a, SEXP max_entries_a){
>    Rcpp::Rcout << "Some Value" << std::endl << 1.23 << std::endl;
>    NumericMatrix S(S_a), W(W_a),Sigma(Sigma_a);
>    NumericVector PD(PD_a),
> PL(PL_a),max_entries(max_entries_a),default_distr(default_distr_a),link_function(link_function_a),calc_rc(calc_rc_a),loss_thr(loss_thr_a);
>    List ret;
> 
> etc
> 
> This still does not print in the console.
> 
> Not sure if I am missing something.
> 
> Thanks and regards,
> 
> On Sat, Dec 17, 2022 at 6:57 PM Rui Barradas <ruipbarradas using sapo.pt> wrote:
>>
>> Às 11:05 de 17/12/2022, Christofer Bogaso escreveu:
>>> Hi Rui,
>>>
>>> Unfortunately, the code Rcpp::Rcout << "---------->>>>>.My values" <<
>>> "\n"; still not printing the value.
>>>
>>> Regarding your second suggestion, R_Print("My values\n"); - where
>>> should I put this statement?
>>>
>>> On Sat, Dec 17, 2022 at 11:39 AM Rui Barradas <ruipbarradas using sapo.pt> wrote:
>>>>
>>>> Às 23:32 de 16/12/2022, Christofer Bogaso escreveu:
>>>>> Hi,
>>>>>
>>>>> I am using an R package where there are some C++ code.
>>>>>
>>>>> To check some intermediate values generated by that C++ code, I added
>>>>> a line like
>>>>>
>>>>> std::cout << "My values";
>>>>>
>>>>> Now with this modification, I next build a modified package (source) using
>>>>>
>>>>> R CMD build
>>>>>
>>>>> Next I install this modified package using install.packages() function
>>>>>
>>>>> However during the run-time of the C++ code with above modification, I
>>>>> dont get any print with "My values"
>>>>>
>>>>> Can you please help to understand why am not getting that printed?
>>>>>
>>>>> ______________________________________________
>>>>> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>> Hello,
>>>>
>>>> If the package uses Rcpp try instead
>>>>
>>>>
>>>> Rcpp::Rcout << "My values" << "\n";   // or std::endl
>>>>
>>>>
>>>> More generally, there is also
>>>>
>>>>
>>>> R_Print("My values\n");
>>>>
>>>>
>>>>
>>>> Hope this helps,
>>>>
>>>> Rui Barradas
>>>>
>>>>
>>>>
>>>>
>>
>> Hello,
>>
>> Put R_Print where your cout is and instead of it.
>>
>> As for Rcpp::Rcout, instead of "\n" try ending the line with std::endl
>> to immediately flush the buffer.
>>
>> Hope this helps,
>>
>> Rui Barradas
>>
>>
Hello,

1. Forget R_print, it is meant for C code, not for Rcpp.
    Besides, it is also an error of mine, I was thinking about Rprintf, 
see below.

2. The following works as expected.
    It's the first example in

vignette("Rcpp-introduction", package = "Rcpp")

    with the if/Rcout and Rprintf instructions added.



File: convolve_rcpp.cpp



#include "Rcpp.h"

using namespace Rcpp;
// [[Rcpp::export]]
NumericVector convolve_cpp(const NumericVector& a, const NumericVector& b) {
   // Declare loop counters, and vector sizes
   int i, j,
	na = a.size(), nb = b.size(),
	nab = na + nb - 1;
	// Create vector filled with 0
	NumericVector ab(nab);
	// Crux of the algorithm
	for(i = 0; i < na; i++) {
		// this works as expected, it prints to the console
		// printing is on every 10 times through the loop
		if(i % 10 == 0)  {
			Rcpp::Rcout << "Some Value " << i << "\n";
			Rcpp::Rcout << "     Value " << a[i] << std::endl;
		}
		for(j = 0; j < nb; j++) {
			ab[i + j] += a[i] * b[j];
		}
	}
	Rprintf("Done\n");
	// Return result
	return ab;
}



Then run the R script


path <- "~/path/to/Rcpp/code"
fl <- list.files(path, pattern = "convolve\\.cpp")
fl <- file.path(path, fl)

Rcpp::sourceCpp(fl)

x <- 1:1e4
y <- 10:1

z <- convolve_cpp(x, y)
str(z)
# num [1:10009] 10 29 56 90 130 175 224 276 330 385 ...


Hope this helps,

Rui Barradas