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
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help