Hi, Does it alleviate things if you rewrite the sums to avoid large products?
For I even: J+I*(N-I/2)-(N-I/2) For I odd: J+I*(N-(I+1)/2)-(N-(I+1)/2)+(I+1)/2 Hope it helps, Tsjerk On Mon, Feb 7, 2011 at 7:21 AM, Berend Hasselman <b...@xs4all.nl> wrote: > > > Earl F Glynn wrote: >> >> >> 2-byte (16 bit) signed integers would have a range from -32768 to >> +37267. So, it looks like you may be using 2-byte integers and 46,300 >> would definitely cause an overflow with 16-bit integers. >> >> I haven't used Fortran for a long time, but there could be a compiler >> switch that forces all 2-byte integers, or a specific declaration that >> says I, J, N, IOFFSET are only 2-byte (16-bit) integers. >> >> I'm guess, but you might try a specification like >> >> INTEGER*4 I, J, N, IOFFSET >> >> assuming INTEGER*4 is legal with your Fortran compiler: >> > > The overflow is not caused by 16 bits integers. > I'm quite sure the OP is using 32 bit integers. > The overflow is caused by the multiplication N*(i-1) and/or i*(i+1). > > In Fortran there's not much you can do about this unless your compiler > supports larger integers. > A pity that fortran doesn't have a posint. > > Either your solution with doubles or a small C function looks like the way > out. > > Berend > -- > View this message in context: > http://r.789695.n4.nabble.com/Fortran-and-long-integers-tp3263054p3263605.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > -- Tsjerk A. Wassenaar, Ph.D. post-doctoral researcher Molecular Dynamics Group * Groningen Institute for Biomolecular Research and Biotechnology * Zernike Institute for Advanced Materials University of Groningen The Netherlands ______________________________________________ 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.
