On 09/12/2011 1:40 PM, Hervé Pagès wrote:
Hi,x<- c(rep(1800000003L, 10000000), -rep(1200000002L, 15000000)) This is correct: > sum(as.double(x)) [1] 0 This is not: > sum(x) [1] 4996000 Returning NA (with a warning) would also be acceptable for the latter. That would make it consistent with cumsum(x): > cumsum(x)[length(x)] [1] NA Warning message: Integer overflow in 'cumsum'; use 'cumsum(as.numeric(.))'
This is a 64 bit problem; in 32 bits things work out properly. I'd guess in 64 bit arithmetic we or the run-time are doing something to simulate 32 bit arithmetic (since integers are 32 bits), but it looks as though we're not quite getting it right.
Duncan Murdoch
Thanks! H. > sessionInfo() R version 2.14.0 (2011-10-31) Platform: x86_64-unknown-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_CA.UTF-8 LC_NUMERIC=C [3] LC_TIME=en_CA.UTF-8 LC_COLLATE=en_CA.UTF-8 [5] LC_MONETARY=en_CA.UTF-8 LC_MESSAGES=en_CA.UTF-8 [7] LC_PAPER=C LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_CA.UTF-8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods base
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