Might have something to do with .Machine$double.eps on the respective
machines.
>From help(.Machine),
double.eps: the smallest positive floating-point number `x' such that
`1 + x != 1'. It equals `base^ulp.digits' if either `base'
is 2 or `rounding' is 0; otherwise, it is `(base^ulp.digits)
/ 2'.
On Friday 31 January 2003 01:14 pm, Bob Gray wrote:
> Does anyone know precisely what is different about the arithmetic
> and/or storage of double precision floating point to produce the
> following differences between the Sun and Windows versions (Splus 6
> on the same Windows 2000 machine gives the same results as Solaris)?
>
> R 1.6.1, Sun Solaris, gcc + an old Sun f77
>
> > options(digits=20)
> > 1+(1/2^53+1/2^106)
>
> [1] 1
>
> > 1+(1/2^53+1/2^105)
>
> [1] 1.0000000000000002
>
> > 1+(1/2^53+1/2^64)
>
> [1] 1.0000000000000002
>
> > 1+(1/2^53+1/2^63)
>
> [1] 1.0000000000000002
>
> R 1.6.1, Windows 2000, binary downloaded from CRAN
>
> > options(digits=20)
> > 1+(1/2^53+1/2^106)
>
> [1] 1
>
> > 1+(1/2^53+1/2^105)
>
> [1] 1
>
> > 1+(1/2^53+1/2^64)
>
> [1] 1
>
> > 1+(1/2^53+1/2^63)
>
> [1] 1.0000000000000002
>
> (This may be frivolous, but I have been using the first 2 lines as an
> example in a course.)
>
> Thanks
> --
> Bob Gray
>
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