[PD] Some more float weirdness/fun

[Martin Peach]

On 2012-03-09 02:32, Roman Haefeli wrote:
> On Thu, 2012-03-08 at 18:03 -0500, Mathieu Bouchard wrote:
>> Le 2012-03-08 à 11:47:00, Jonathan Wilkes a écrit :
>>
>>>> From: Roman Haefeli<reduzent at gmail.com>
>>>> That's a good example of the implications inherent in floats. What you
>>>> call a work-around is actually the correct solution. When counting, make
>>>> sure you count with something that can precisely represented by floats,
>>>> otherwise the error will grow with each iteration. Integers up to
>>>> 1.6*10^7 meet that criterion.
>>> Is this still an issue when float precision is 64-bit?
>>
>> in float32 you have 24 significant bits.
>> in float64 you have 53 significant bits.
>>
>> This means that the limit is pushed back from 16777216 to 9007199254740992
>> instead.
>
> But 0.1 still cannot be represented exactly by float64, can it?

For any floatX unless X is infinity the number of floats that are not 
exactly represented is always infinite.

Martin