If you take a look at the code, there is something fishy. Add the
following statements.
def sum_of_squares(p):
if p.mod(4)==1:
A=startingA(p)
print A
B=1
temp = A**2+B**2
print type(A**2+B**2)
temp
M=(A**2+B**2)/p
while M>1:
[a,b,r]=iterate(A,B,M,p)
[A,B,M]=[a,b,r]
return [A,B]
else:
print 'no'
For 73 you get
46
<type 'sage.rings.finite_rings.integer_mod.IntegerMod_int'>
Traceback (click to the left of this block for traceback)
...
ZeroDivisionError: Inverse does not exist.
So A^2+B^2 (legitimate syntax in Sage) is a modular integer. In fact,
you can check that its modulus is 73, and so it's no surprise that
dividing by 73 \equiv 0 will result in a zero-division error.
You'll have to find a way to get the power modulo p without actually
making the thing an integer mod p.
Hope this helps!
- kcrisman
On Jun 22, 7:43 pm, Ken Levasseur <[email protected]> wrote:
> On Jun 22, 4:06 pm, Robert Bradshaw <[email protected]>
> wrote:
>
> > What is startingA ? What is the parent of A?
>
> The full .sws file is athttp://homepage.mac.com/klevasseur/sum_of_squares.sws
>
> Ken
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