Robert,
I don't understand what you suggest.
Try the following:
replace the line 10222 of sage/graphs/generic_graph.py
with
sage: abs(M.determinant())
(the original line does not have abs()) and run
sage -t -long "devel/sage/sage/graphs/generic_graph.py"
You should see the result above.
(sorry, I tried to make a short test to show this, but I can't: there
might be some imports involved that might affect this...)
Dima
On Feb 3, 10:43 am, Robert Bradshaw <rober...@math.washington.edu>
wrote:
> On Feb 2, 2010, at 6:32 PM, David Joyner wrote:
>
> > On Tue, Feb 2, 2010 at 9:26 PM, Dima Pasechnik <dimp...@gmail.com>
> > wrote:
> >> ...
> >> sage: abs(M.determinant())
> >> Expected:
> >> 712483534798848
> >> Got:
> >> 7.12483534798848e14
>
> > I vaguely remember that M.det() is only well-defined up to sign.
> > You could rewrite the test to avoid abs, but I'm wondering if abs is
> > the
> > reason scientific notation is used here. Do you know?
>
> I think using abs is the clearest for something that's only defined up
> to sign. As for the scientific notation, what's it returning here? Try
> putting parent(M.det()) or type (M.det()) into the doctest. The
> absolute value of integers *should* return integers...
>
> - Robert
>
> sage: z = -3**500; z
> -36360291795869936842385267079543319118023385026001623040346035832580600191
> 583895484198508262979388783308179702534403855752855931517013066142992430916
> 562025780021771247847643450125342836565813209972590371590152578728008385990
> 139795377610001
> sage: abs(z)
> 363602917958699368423852670795433191180233850260016230403460358325806001915
> 838954841985082629793887833081797025344038557528559315170130661429924309165
> 620257800217712478476434501253428365658132099725903715901525787280083859901
> 39795377610001
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