Re: [WWdevel] Subtractive cancellation

[Davide P.C. <dp...@un...>]

> I'm afraid I'm going to sully your elegant explanation with a stupid 
> question.  I (believe I) understand the issue of cancellation, however 
> poor I may be at predicting it.  In the example problem that we 
> discussed before you sent this e-mail, I found that the issue with 
> subtractive cancellation occurred when I used the Parser version of 
> fun_cmp, but not the older version.  Is there any reason besides blind 
> luck that the older version didn't also mis-grade the problem?

Yes, there is a reason:  the two versions of the checker pick the 
random points differently (it is a simple matter of the order in which 
things are done, so the random numbers you get are different in the two 
orders), so when you switch to the older checker, the chances are you 
don't get the point near the origin that is the one that has the 
instability.

Davide