Re: Floating Point Approximations.

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Thu, 29 Mar 2007 01:38:27 GMT
Message-ID: <nMEOh.16763$PV3.172916_at_ursa-nb00s0.nbnet.nb.ca>

paul c wrote:

> Bob Badour wrote:
> 

>> paul c wrote:
>>
>>> Bob Badour wrote:
>>>
>>>> ...
>>>> The epsilon would be 16 times larger for BCD floats.
>>>> ie. 5e-7 versus 2^-25
>>>
>>> Sorry, not hip to epsilon in this context. Does the above correspond
>>> with 50 millionths versus 32 millionths, or thereabouts?
>>
>> Nope: 0.5 millionths versus 0.0298 millionths scaled by the exponent
>> part of the float.
>>
>> For floating point representations, epsilon is the rounding factor,
>> which is half the least significant digit of the mantissa. If I recall
>> correctly, a 32-bit BCD float has a 6 decimal digit mantissa with a 2
>> decimal digit exponent. A 32-bit binary float has a 24 bit mantissa
>> with an 8 bit exponent.
>
> Sorry, forgot to ask - I assume you're talking about IBM BCD mantissa?

The only BCD float I have used was the one that came with Microsoft's "Business Basic" circa 1987. I assume other BCD floats will be similar; although, I haven't studied them at all. Received on Thu Mar 29 2007 - 03:38:27 CEST