[Rcpp-devel] Data Persistence when using inline
noahsilverman at ucla.edu
Thu Sep 8 00:04:18 CEST 2011
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.)
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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