Hi all, I'm hoping someone more knowledgeable in Fortran than I can chime in with opinion.
I'm the maintainer of the flashClust package that implements fast hierarchical clustering. The fortran code fails when the number of clustered objects is larger than about 46300. My guess is that this is because the code uses the following construct: IOFFSET=J+(I-1)*N-(I*(I+1))/2 where N is the number of clustered objects and I, J can vary between 1 and N. The result is used as index to access an array (namely the distance structure). When N is more than 46341 (or 2^16/sqrt(2)), the expressions I*(I+1) and (I-1)*N can overflow and turn negative, messing up the indexing and crashing the code and the entire R session with a segmentation fault. My solution is to turn the integers into double precision's, calculate the index and convert back as follows: XI = DBLE(I) IOFFSET=J+NINT( (XI-1)*N - (XI*(XI+1))/2) I'm wondering if there's a better way, something along the lines of unsigned and/or long integers that are available in C? Thanks, Peter ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
