On 31 October 2015 at 19:08, Alessandro Mammana wrote:
| Dear All,
| When creating a large matrix with the follwing code:
|
| #include <Rcpp.h>
| // [[Rcpp::export]]
| Rcpp::IntegerMatrix makeMat(int nrow, int ncol){
| Rcpp::IntegerMatrix mat(nrow, ncol);
| return mat;
| }
|
| I get the error:
|
| Error in .Primitive(".Call")(<pointer: 0x7f86936d3ea0>, nrow, ncol) :
| negative length vectors are not allowed
|
| Where nrow*ncol is a very large number (about 3*10^9). I understand
| that such a number cannot be represented by an int type, but this does
| not seem to be a problem when in R I do:
|
| > mat <- matrix(0, nrow=nrow, ncol=ncol)
|
| Questions:
| 1. why is the behaviour different between R and Rcpp in the allocation
| of a matrix?
| 2. In a 64 bits machine, what is actually the maximum allowed length
| of a vector/matrix? does the length of a vector/matrix need to be
| represented by an int?
Support for large objects is reasonably new in Rcpp -- it only came with the
0.12.0 release thanks to a lot of work by Qiang.
So what we have here is a bug. You could ensure your spot in the hall of
fame by debugging and fixing it :)
FWIW I can tickle the bug in NumericMatrix too. Allocating a matrix of 3e6 *
1e4 takes a hell of time even on the largest machine I have (easy) access too
at work --- which is not exactly a lightweight at 1/4 TB of RAM ...
So your help in debugging would be appreciated.
Dirk
--
http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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