Re: [Valgrind-developers] Precision in vcpu_fnfns

[Nicholas N. <n.n...@gm...>]

On Thu, Feb 26, 2009 at 5:52 AM, Ivan Jager <aij...@an...> wrote:
>>
>> I propose changing the test to omit the +/- at the start of the
>> answers (to remove +0 and -0 differences), to print 12 decimal places
>> rather than 13 (to remove the difference in the 13th decimal place),
>> and possibly to filter the sign of the exponent if its zero (to remove
>> the difference between 1.0000e-00 and 1.0000e+00).
>
> Ok, what am I missing? IIRC the exponent part of an IEEE FP number is
> represented by an integer, where the exponent is calculated by taking that
> integer as unsigned and subtracting a constant. So, how is it possible to
> have a different representation for 1.0000e-00 and 1.0000e+00?

I don't know.  Something in the printf() implementation?

> Out of curiosity, are you encountering the differences on PPC or on an x86
> Mac? The only thing I can think of which could cause a diffirence on x86
> would be the compiler, since on Linux/x86 at least GCC defaults to not using
> -ffloat-store. If I understand correctly, compiling the tests with
> -ffloat-store should produce the same results as on any sane architecture,
> however that would also mean the tests wouldn't be testing the extended
> precision part of Valgrind/x86.

x86 Mac.

N