Re: [PyGiNaC-users] strange behavior with the test suite

[Jonathan B. <jbr...@ea...>]

On Tue, 2005-10-04 at 20:14 +0300, Matti Peltom=E4ki wrote:
> Hi,=20
>=20
> > I think that this is a canonicalization issue.  If hash(x) is greater
> > than hash(y) (when reinterpret_cast'ed back to unsigned ints), then
> > pow(x - y, 2) normalizes to pow(y - x, 2)
> >=20
> > I'm not sure if this behavior is deliberate so I'm bringing it up on
> > ginac-list.  In the meantime, a patch has been committed to CVS that
> > works around the error.
>=20
> I'm afraid there is something wrong in the workaround. I did a cvs update=
=20
> getting your changes (bin/exam_normalization.py and ChangeLog) and rerun=20
> the test (again several times since it does not fail every time), and I=20
> still get the error sometimes.=20
>=20
> Are you still able to reproduce the error or is it just me?=20

I guess I didn't run the test often enough before I committed the fix
last night, because you are right.  Whatever the cause of the error, I'm
inclined to let it slide since this is mathematically correct, and
because (pow(x-y, 2)/pow(y-x,2)).normal() evaluates to numeric(1).

In the current fix, if the test fails one way, it is retried with the
second option.

-Jonathan