[Cfp-interest 2045] Re: Underflow

[Fred J. Tydeman]

On Thu, 1 Jul 2021 21:01:44 -0700 Jim Thomas wrote:
>
>> I would prefer:
>> 
>> [6] The result underflows if a nonzero result value, before rounding,
>> would have magnitude (absolute value) less than the minimum normalized
>> number in the type.249
>
>This seems to assume a model where a wider precision result is computed and then rounded to the result format. C 
>doesn't have that model for math functions.

Both
  Float from Float * Float, eg (MinFloat*(1.f+FLT_EPSILON))  *  ( 1.f - FLT_EPSILON)  is MinFloat after rounding
  Float from Float / Float
Are not wider precision (everything done as Float), but have a rounding.

>> Also, I believe that "inexact" should be added to the footnote as:
>> 
>> 249)The term underflow here is intended to encompass both "gradual
>> underflow" as in IEC 60559 and also "flush-to-zero" underflow. IEC
>> 60559 underflow can occur in cases where the magnitude of the inexact
>> rounded result equals the minimum normalized number in the format.
>
>Change "the inexact" to "an inexact".

OK


---
Fred J. Tydeman        Tydeman Consulting
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