[Rd] Parallel R expression evaluations

[JaiReddy]

Hi all,

I am using R-3.0.1 under Linux platform to embed R into my C++ code.

I am facing an error while executing more than 1 R-expressions parallelly.

I am executing round(X) and abs(X) parallelly on a set of 50 input rows 
which resulted in segmentation fault after getting the following errors.

Error: unprotect_ptr: pointer not found
Error: argument to 'findVar' is not an environment

I am using the following code snippet for initializing R, parsing and
evaluation of R expression

// For initialization

        int res= Rf_initEmbeddedR(R_argc, (char**)R_argv);

// For parsing and evaluation

        SEXP cmd1= Rf_mkChar(rscript);
	SEXP cmdSexp, cmdexpr, sresult = R_NilValue;
	ParseStatus status;
	R_len_t i=0;

	PROTECT(cmdSexp = Rf_allocVector(STRSXP, 1));
	SET_STRING_ELT(cmdSexp, 0, cmd1);
	// parsing vector for R expressions
	cmdexpr = PROTECT(R_ParseVector(cmdSexp, -1, &status, R_NilValue));
	if (status != PARSE_OK) {
		UNPROTECT(2);
		// error handling
		return;
	}
	
	for(i = 0; i < Rf_length(cmdexpr); i++)
	{
		int error;
		sresult = R_tryEval(VECTOR_ELT(cmdexpr, i), R_GlobalEnv, &error);	// R
expression evaluation 
		if(error)		// checking for error
		{
			// error handling
			return;
		}
	}
	UNPROTECT(2);


I wonder if R supports parallel evaluations within a single session. I have
seen parallel evaluations of R using Rserve package. As I am trying to
overcome the overhead (using Rserve) in creating new connection for each
evaluation, here I am trying using embeded R.

I tried Rf_endEmbeddedR each time after one evaluation and initializing R
for the next set of evaluation. Even that did't work.

Please suggest me possible solution if any.

Thanks in advance.

Jai
 




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