Re: Re[2]: III_requantize() accuracy

On Mar 24, 2004, at 5:36 PM, Grigory A. wrote:
>> Keeping in mind that 2^(-36.75) = 2^(-36) × 2^(-3/4), you will find 
>> that III_requantize(210, -147) calculates:
>>
>>               210^(4/3)    ⇒ 0x04e0393e × 2^12
>>    0x04e0393e × 2^(-36+12) ⇒ 0x00000005
>>                 2^(-3/4)   ⇒ 0x09837f05
>>    0x00000005 × 0x09837f05 ⇒ 0x00000002
>
> Yes I am agree. Only one difference in my calculation scheme I firs 
> multiply on root - in this case 2^(-3/4) and next rounding and 
> shifting. This small changes give more precise result.

You make a good point. The accuracy can indeed be improved by 
multiplying the root first, before losing significant digits from the 
shift.

This probably merits a change for the next release.

Thanks,

-- 
Rob Leslie
[email protected]