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
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