R help - May 2009 - 64 bit R double precision

Hi,

If R is compiled for a 64 bit platform, does the double data type make 
use of the additional precision or is it set at a fixed length?

Thanks,

Paul

On 5/7/2009 12:56 PM, Paul Emberson wrote:
> Hi,
> 
> If R is compiled for a 64 bit platform, does the double data type make 
> use of the additional precision or is it set at a fixed length?
It is still a 64 bit floating point value.  R may use "long double" 
internally for some calculations, but the numeric type that is saved 
doesn't change.

Duncan Murdoch

Paul Emberson wrote:
> Hi,
> 
> If R is compiled for a 64 bit platform, does the double data type make 
> use of the additional precision or is it set at a fixed length?
No. Double is double, 64 bits, although sometimes 80 bits when things 
are kept in registers. However, even though the FPU is identical between 
64 and 32 bit machines, you do not in general get the same results, due 
to tricks played by optimizing compilers.

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