#6391: libGAP! -- create a Cython library interface to gap
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Reporter: was |
Owner: was
Type: enhancement |
Status: needs_review
Priority: major |
Milestone: sage-5.3
Component: group theory |
Resolution:
Keywords: |
Work issues:
Report Upstream: N/A |
Reviewers: Dima Pasechnik, Ivan Andrus, Volker Braun, William Stein
Authors: Dima Pasechnik, Ivan Andrus, Volker Braun, William Stein |
Merged in:
Dependencies: #13211 |
Stopgaps:
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Comment (by vbraun):
After considerable despair I finally realized that Python called the
libgap initialization from a higher stack frame than where `c.Order()` was
executing. One peculiarities of the GAP memory manager is that it trawls
the stack for pointers into its memory pool and keeps these alive (so you
can just work with local stack-allocated GAP objects and not worry). While
its easy to figure out the highest stack frame (its you, the currently
executing function) we must take care to inform GAP about the lowest stack
frame that can hold a pointer to a memory bag!
Now Miguel's example runs perfectly! For the record, you can use the
following syntactic sugar to make the code look nicer:
{{{
sage: G =libgap.FreeGroup(2)
sage: a,b = G.GeneratorsOfGroup()
sage: rel = libgap([a^2, b^2, a*b*a*b])
sage: H = G / rel
sage: c = H.GeneratorsOfGroup()[0]
sage: for i in range(300000):
... n = c.Order()
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6391#comment:83>
Sage <http://www.sagemath.org>
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