#11754: Computation of rank-decompositions in Sage
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Reporter: ncohen | Owner: jason, ncohen, rlm
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.0
Component: graph theory | Keywords:
Work_issues: | Upstream: N/A
Reviewer: David Coudert | Author: Nathann Cohen
Merged: | Dependencies:
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Changes (by dcoudert):
* status: needs_review => needs_work
Comment:
Good news, I have identified the cause of my segfault !
In function `init_rw_dec`, with N=30, I have `sizeof(subset_t) * (1ul <<
n) == 0` !!!
Consequently, the malloc function returns a pointer.
This is a stupid numerical problem.
We have `sizeof(subset_t)==4` and `(1ul<<30)==1073741824`. But at least on
my computer, it happens that `4294967296==0 mod(2^32)`...
So you should add a test like this just after the malloc:
{{{
if((sizeof(subset_t) * (1ul << n)==0) && (n>0) && cslots) return(-1);
}}}
A similar test in function `init_rw` could be safer.
No news concerning the compilation error.
Best,
D.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11754#comment:34>
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