#20447: Wrong result from delsarte_bound_additive_hamming_space with GLPK exact
simplex
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Reporter: mkoeppe | Owner:
Type: defect | Status:
Priority: major | needs_info
Component: coding theory | Milestone: sage-7.2
Keywords: lp | Resolution:
Authors: | Merged in:
Report Upstream: Not yet reported upstream; | Reviewers:
Will do shortly. | Work issues:
Branch: | Commit:
Dependencies: #20406 | Stopgaps:
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Comment (by dimpase):
Replying to [comment:5 mkoeppe]:
> How come you never run into trouble with the floating-point based
solvers with this kind of code?
of course I did, and docs explicitly say that as soon as you specify
another solver, you are on your own.
{{{
- solver – the LP/ILP solver to be used. Defaults to PPL. It is arbitrary
precision, thus there will be no rounding errors. With other solvers (see
MixedIntegerLinearProgram for the list), you are on your own!
}}}
>
> It is certainly ironic that the exact solver has more floating-point
fuzz than the floating-point solvers. But your code cannot be correct if
solver is a floating-point solver.
I don't think there is an API to check whether a solver is exact, and so I
never bothered to check this in the code.
>
> And there is an apparent upstream issue with GLPK. I wouldn't call it a
bug, but given the design decision to return the exact values as double-
floats, it should at least be improved to return all integers that have an
exact representation in double-float as such.
>
this design is called lazyness, in CS, and not only :-)
--
Ticket URL: <http://trac.sagemath.org/ticket/20447#comment:6>
Sage <http://www.sagemath.org>
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