[Rcpp-devel] Data Persistence when using inline
noahsilverman at ucla.edu
Thu Sep 8 00:12:47 CEST 2011
UCLA Department of Statistics
8117 Math Sciences Building #8208
Los Angeles, CA 90095
On Sep 7, 2011, at 3:04 PM, Noah Silverman wrote:
> Maybe I didn't explain it well enough. The question absolutely pertains to using the inline functionality.
> As each new data arrives, I want to pass it to my C++ function. If this were a pure C++ implementation, then I would just append an STL vector and pass a pointer of that vector to the function. However, since this is R, I don't see how to do that. I can, of course, keep a vector in R and pass the entire vector to the C++ function. That will, however slow things down significantly.
> Ultimately, I'dl like to have R pass each new data point to the C++ function, and have that function manage keeping the appropriate length window of past data points. (Again, trivial to do in pure C++).
> This really is an issue of persistent object and passing between R and C++. I want a persistent C++ vector, not an R data structure. (Having C++ manage the vector will be much faster.)
> Noah Silverman
> UCLA Department of Statistics
> 8117 Math Sciences Building #8208
> Los Angeles, CA 90095
> On Sep 7, 2011, at 2:56 PM, Dirk Eddelbuettel wrote:
>> On 7 September 2011 at 14:46, Noah Silverman wrote:
>> | Hi,
>> | I'm writing a function using Rcpp through inline. This function will be a
>> | filter on an incoming data stream.
>> | I need to keep the past several data values so that they are accessible to the
>> | function each time it is called. This is easy to do with a data structure in
>> | R (and then passing subsequent structure to the C++ function) but that seems
>> | rather slow. Is there some way to define a persistent object that is
>> | accessible to an Inline function using Rcpp?
>> | If the code was in pure C++, it would be trivial to have an object and then
>> | just pass a pointer to that object. I can't figure out how to do the same
>> | thing with R+Rcpp+inline.
>> i) Read up on the 'static' argument for variable declarations in C and C++.
>> ii) Rethink your architecture, maybe have an 'agent' operate on the stream
>> and report to a persisting 'broker' that keeps state.
>> iii) Read up on persisting data as a general issue.
>> This has little to do with Rcpp and your preference of inline over packages,
>> but rather with how to think in code (and/or C++) and that is NOT a topic
>> covered on this list.
>> Let's please try to keep focus on Rcpp and related questions here.
>> | Thanks!
>> | --
>> | Noah Silverman
>> | UCLA Department of Statistics
>> | 8117 Math Sciences Building #8208
>> | Los Angeles, CA 90095
>> | ----------------------------------------------------------------------
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