| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
On 01/01/2014 06:21, Dmitry Nadezhin wrote:
My understanding is that the purpose of a particular choice of T-hull among different minimal enclosure in implicit types was for debugging and for reproducibility.
We don't need T-hull for debugging and reproducibility. A simple sentence such as "Given the same inputs, operations at level 2 shall always return the same outputs" would be sufficient for that purpose. Knowing that there exists some theoretical T-hull function does not bring any additional help for debugging purpose.
The tightest accuracy mode is required only for basic operations (add,sub,mul,div,sqrt,fma) and for some other "easy" operations. For other operations like "cospi", only valid accuracy mode required. It seems that there is no even a requirement that valid result must contain T-hull of exact result. It may be another minimul enclosure or non-minimal enclosure. Hence, it is possible to design a conforming implementation.
You might have missed my point. I am not saying that it is not possible to design a div function that returns a T-hull. What I am saying is that it is might be impossible to design some add, sub, mul, div, sqrt, fma, conversion functions that share the same T-hull function. The important word here is "share".
Indeed, as currently worded, the document forces all the functions to use the same definition of T-hull (rather than one per operation, for instance). Do you (or anyone else) know of a mid-rad library that guarantees this property?
Best regards, Guillaume