[Rcpp-devel] Rcpp:wrap - any limitations for vector size?

[Mathias Bader]

 Hello

 I am working with Rcpp as part of my master thesis to speed up an MCMC 
 simulation. I happen to have a wired bug which I am trying to find for 
 some days now and I think I narrowed it down to the part of the code, 
 where C++ returns a list back to R.
 I can output the list in C++ before returning it, everything looks fine 
 then. When trying to output the same data after receiving it in R, R 
 Studio crashes.

 I am connecting R and C++ using the following code:

 # define the C++ compiled function for the MCMC simulation
 require('inline')
 settings <- getPlugin("Rcpp")
 settings$env$PKG_CXXFLAGS <- paste("-I", getwd(), sep="")
 src_dppc <- paste(readLines("dppClustering.cpp"), collapse="\n")
 header_includes <- paste(readLines("headerIncludes.h"), collapse="\n")
 compiledClustering <- cxxfunction(signature(
   R_data="numeric",
   R_initial_point_assignment="numeric",
   R_alpha="numeric",
   R_mcmc_steps="integer",
   R_sd_min="numeric",
   R_next_cluster_index="integer",
   R_cluster_index_mapping="numeric",
   R_cluster_ids="numeric",
   R_cluster_ids_silhouette_values="numeric",
   R_performed_steps_count="integer",
   R_likelihood_method="character"
 ), src_dppc, plugin="Rcpp", settings=settings, 
 includes=header_includes)



 The call in R looks as follows:

 # perform clustering
 results <- compiledClustering(
   R_data                     = data,
   R_initial_point_assignment = d$final.clustering,
   R_alpha                    = dppc.config.alpha,
   R_mcmc_steps               = steps.to.perform,
   R_sd_min                   = dppc.config.sd.min,
   R_next_cluster_index       = d$next.cluster.index,
   R_cluster_index_mapping    = d$cluster.index.mapping,
   R_cluster_ids              = as.vector(t(d$cluster.ids)),
   R_cluster_ids_silhouette_values = d$cluster.ids.silhouette.values,
   R_performed_steps_count    = d$performed.steps.count,
   R_likelihood_method        = d$method.to.use
 )


 If I try to output the returned list after that call using 
 "cat(results)", it will output the returned list till the third last 
 element. From that element it outputs only the name of the element, but 
 not the value and then it crashes before outputting the last two 
 elements. Always at that point.
 In my C++ code I create the return value using the following code:


 // create return object
 Rcpp::List results = Rcpp::List::create(
 	Named("clusterAssignment")          = wrap(r_cluster_assignment),
 	Named("debugOutput")                = wrap(r_debug_output),
 	Named("clusterCountIncreases")      = wrap(r_cluster_count_increases),
 	Named("clusterCountDecreases")      = wrap(r_cluster_count_decreases),
 	Named("dataMovementPointIndices")   = 
 wrap(r_data_movement_point_indices),
 	Named("dataMovementNewClusters")    = 
 wrap(r_data_movement_new_clusters),
 	Named("clusterIndexMappingRev")     = 
 wrap(r_cluster_index_mapping_rev),
 	Named("nextClusterIndex")           = 
 wrap(r_next_cluster_index_return),
 	Named("clusterCounts")              = wrap(r_cluster_counts),
 	Named("McmcClusterIds")             = wrap(r_mcmc_cluster_ids),
 	Named("clusterIds")                 = wrap(r_cluster_ids),
 	Named("clusterIdsSilhouetteValues") = 
 wrap(r_cluster_ids_silhouette_values)
 );


 My question: Is there any restriction on the size of the vectors which 
 I hand from C++ to R? Because during the MCMC simulation the vectors 
 might become really big.

 Thank you very much
 Mathias