Re: Precision on a Mac?

[Dmitri A. Sergatskov]

On 12/15/06, Vic Norton <address@hidden> wrote:
> Results from GNU Octave, version 2.9.9 on Mac OS X 10.4.8, PowerPC G5:
> u = eps/2 = 1.1102e-16
> eps = 2.2204e-16
> u is the unit roundoff of Golub & Van Loan, Matrix Computations:
>    1 + u == 1 is true
>    1 + eps > 1 is true
> precision for base = 2 (Golub & Van Loan):
>    precision_round = 1 - log(eps)/log(2) = 53
>    precision_trunc = 1 - log(u)/log(2) = 54
>
> Does this mean that my Mac uses 53 bits for the "precise" part of a floating 
> point number and 11 bits for its sign and exponent? I guess I am using 64-bit arithmetic.

IEEE standard for 64-bit floating point arithmetic uses 52 bits for
the mantissa, 11 for
the exponent and 1 for the sign.

> Thanks for your input.
>
> Vic

Sincerely,

Dmitri.
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