BUG in handling errors from gap
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Vít Tuček
Feb 21, 2018, 10:47:04 AM2/21/18
to sage-devel
If you try to test for equality in a finitely presented groupy the sage kernel can crash.
The following real life example leads to restarted kernel in the notebook interface and to "gap: cannot extend the workspace any more!" in Sage terminal interface (and nongraceful exit).
k = 3
p = 18
d = 2*p/(p-6)
l = 2*p*k/(p*k-2*k-2*p)
F.<J,P,R1,R2>=FreeGroup()
G = F / [J^3, P^(3*d), R1^p, R2^p, (F([-2,1]))^k, (F([4,3,1]))^l, F([-4,2,3,-2]), F([-4,1,3,-1]), F([-2,3,4])]
k = G.rewriting_system()
x = k.reduce(P^8)
y = k.reduce(G([-4,2,3]))
t = k.reduce(x*y)
The following real life example leads to restarted kernel in the notebook interface and to "gap: cannot extend the workspace any more!" in Sage terminal interface (and nongraceful exit).
k = 3
p = 18
d = 2*p/(p-6)
l = 2*p*k/(p*k-2*k-2*p)
F.<J,P,R1,R2>=FreeGroup()
G = F / [J^3, P^(3*d), R1^p, R2^p, (F([-2,1]))^k, (F([4,3,1]))^l, F([-4,2,3,-2]), F([-4,1,3,-1]), F([-2,3,4])]
k = G.rewriting_system()
x = k.reduce(P^8)
y = k.reduce(G([-4,2,3]))
t = k.reduce(x*y)
Vít Tuček
Feb 21, 2018, 10:52:59 AM2/21/18
to sage-devel
I forgot the last line
t == G.one()
The ticket https://trac.sagemath.org/ticket/14779 seems to be related.
Dne středa 21. února 2018 16:47:04 UTC+1 Vít Tuček napsal(a):
t == G.one()
The ticket https://trac.sagemath.org/ticket/14779 seems to be related.
Dne středa 21. února 2018 16:47:04 UTC+1 Vít Tuček napsal(a):
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