[R] accuracy of test cases

[Uwe Ligges]

Robin Hankin wrote:

> 
> On Apr 29, 2005, at 11:51 am, Uwe Ligges wrote:
> 
>> Robin Hankin wrote:
> 
> 
> [snip]
> 
>>> The tolerance should be as small as possible, but If I make it too 
>>> small, the test may fail
>>> when executed on a machine with different architecture from mine.
>>> How do I deal with this?
>>
>>
>> See ?all.equal
>>
>> Uwe Ligges
>>
> 
> Hi Uwe
> 
> Thanks for this.  But sometimes my tests fail (right at the edge of a 
> very wibbly wobbly
> function's domain, for example) even with all.equal()'s default tolerance.
> 
> Maybe I should only include  tests where all.equal() passes 
> "comfortably" on my
> machine, and have done with it.  Yes,  this is the way to think about it: I
>  was carrying out tests where one might
> expect them to fail (entrapment?).  My mistake was to focus on the 
> magnitude of
> "tol" and to blithely include tests  where all.equal() failed, or came 
> close to failing.
> 
> Unfortunately, all the interesting stuff happens at the boundary.
> 
> I guess (thinking about it again) that in such circumstances, there is 
> no generic answer.

[We might want to move to R-devel for further discussion...]

Yes, of course the cases at the boundary are the interesting ones.
Unfortunately, it is extremely hard (even if underlying algorithms are 
known - and if possible at all) to calculate the "expected" inaccuracy, 
if algorithms are becoming quite complex.

It would also be possible to intentional include a test that gives 
differences - don't know what Kurt et al. think about it (if we are 
talking about a CRAN package), though.

Best,
Uwe


> 
> best wishes
> 
> rksh
> 
> 
> 
> 
> 
> -- 
> Robin Hankin
> Uncertainty Analyst
> Southampton Oceanography Centre
> European Way, Southampton SO14 3ZH, UK
>  tel  023-8059-7743