Hello,
I found a bug that occurs when calling random_element() on a
polynomial or power series ring over a Givaro finite field (the Givaro
finite fields are used when the field is non-prime and has cardinality
< 2^16). The problem is that the polynomial ring assumes that its
base ring's random_element() method takes arguments and it thus
calls the base ring method like this: R.random_element(*args,
**kwds). But the Givaro FF implementation of random_element() only
takes a 'self' argument, and thus raises a TypeError if args is non-
empty. For example:
--BEGIN--
sage: P.<x> = PowerSeriesRing(GF(3^3, 'a'))
sage: P.random_element(7)
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/hlaw/sage/devel/<ipython console> in <module>()
/Users/hlaw/sage/local/lib/python2.5/site-packages/sage/rings/
power_series_ring.py in random_element(self, prec, bound)
544 1/15 + 19/17*t + 10/3*t^2 + 5/2*t^3 + 1/2*t^4 +
O(t^5)
545 """
--> 546 return self(self.__poly_ring.random_element(prec,
bound), prec)
547
548 def __cmp__(self, other):
/Users/hlaw/sage/local/lib/python2.5/site-packages/sage/rings/
polynomial/polynomial_ring.py in random_element(self, degree, *args,
**kwds)
770 """
771 R = self.base_ring()
--> 772 return self([R.random_element(*args, **kwds) for _ in
xrange(degree+1)])
773
774 def _monics_degree( self, of_degree ):
TypeError: random_element() takes no arguments (1 given)
--END--
In this case, the problem occurs because the
PowerSeriesRing_generic.random_element() passes bound to
PolynomialRing_general.random_element() where it is placed in the
args parameter and subsequently given to
FiniteField_givaro.random_element() which is not expecting any
arguments.
I fixed this problem by adding *args and **kwds parameters to
FiniteField_givaro.random_element():
diff -r 717c10d9cd4a sage/rings/finite_field_givaro.pyx
--- a/sage/rings/finite_field_givaro.pyx Fri Jul 11 11:46:02 2008
-0700
+++ b/sage/rings/finite_field_givaro.pyx Mon Aug 18 16:10:50 2008
+0200
@@ -358,7 +358,7 @@ cdef class FiniteField_givaro(FiniteFiel
else:
return True
- def random_element(FiniteField_givaro self):
+ def random_element(FiniteField_givaro self, *args, **kwds):
"""
Return a random element of self.
Depending on your policy for the random_element() interface, this
may or may not be the best way to fix the problem. The diff above was
against Sage 3.0.5, though I checked that this issue is still present
in 3.1.1.
Regards,
Hamish.
--
Hamish Ivey-Law
PhD student,
Institut de Mathématiques de Luminy, Université de la Méditerranée,
and
School of Mathematics and Statistics, University of Sydney.
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