I am trying to compute the homfly polynomial of some links, given as braids, and I am running in some problems.
For example:
b = [3, 2, 1, 6, 5, 4, 3, 2, -3, -4, 3, -7, 5, 4, 7, -2, -3, -4, -5, -6, -1, -2, -3, -4, -5, -6, -7, 7]
Br = BraidGroup(8)
B = Br(b)
L = Link(B)
L.homfly_polynomial()
and I get the following error:
---------------------------------------------------------------------------
SignalError Traceback (most recent call last)
<ipython-input-7-b500a53dcd1e> in <module>()
3 braidd = Br(b)
4 linkk = Link(braidd)
----> 5 linkk.homfly_polynomial()
/home/user/SageMath/local/lib/python3.7/site-packages/sage/knots/link.py in homfly_polynomial(self, var1, var2,
normalization)
2630 s += ' {} {}'.format(i, cr)
2631 from sage.libs.homfly import homfly_polynomial_dict
-> 2632 dic = homfly_polynomial_dict(s)
2633 if normalization == 'lm':
2634 return L(dic)
/home/user/SageMath/local/lib/python3.7/site-packages/sage/libs/homfly.pyx in
sage.libs.homfly.homfly_polynomial_dict (build/cythonized/sage/libs/homfly.c:1471)()
98 link = str_to_bytes(link)
99 cdef Term ter
--> 100 sig_on()
101 cdef Poly* c_output = homfly(link)
102 sig_off()
SignalError: Segmentation fault
The problem seems to be with some specific diagram of the 2 components unlink (as the one in the previous example). Also, my memory goes up like crazy after trying to compute the homfly polynomial of these particular diagrams/braids.
