Dear sage-support team,
i met a very strange error of Singular under Sage.
The error only occured after doing some other computations. I'm afraid
the complete code would be too long, but I'll try to extract the parts
of my computation that are relevant to the problem, which will take a
while.
Essentially, i computed the cohomology ring of some finite p-Group,
and the cohomology ring is given as a non-commutative ring (Singular)
with a relation ideal.
Afterwards, i did the following:
sage: R=singular.ring(5,'(x(1..8))','(a(2,2,2,2,1,1,3,3),dp)')
sage: singular.LIB("ncall.lib")
sage: S=singular.SuperCommutative(5,8)
sage: singular.setring(S)
sage: S
// characteristic : 5
// number of vars : 8
// block 1 : ordering a
// : names x(1) x(2) x(3) x(4) x(5) x(6) x(7) x(8)
// : weights 2 2 2 2 1 1 3 3
// block 2 : ordering dp
// : names x(1) x(2) x(3) x(4) x(5) x(6) x(7) x(8)
// block 3 : ordering C
// noncommutative relations:
// x(6)x(5)=-x(5)*x(6)
// x(7)x(5)=-x(5)*x(7)
// x(8)x(5)=-x(5)*x(8)
// x(7)x(6)=-x(6)*x(7)
// x(8)x(6)=-x(6)*x(8)
// x(8)x(7)=-x(7)*x(8)
// quotient ring from ideal
_[1]=x(6)^2
_[2]=x(5)^2
Hence, Singular forgot the two further relations x(8)^2 and x(7)^2.
Now, after singular.quit(), the above example worked perfectly. Hence,
it seems that i menaged to do harm to Singular by my cohomology ring
computations.
Do you know of any "dangerous" commands that can cause Singular to
start to compute nonsense? Perhaps an answer would simplify my attempt
to detect an error in my code.
Yours sincerely
Simon
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