#12220: Updated CBC spkg
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Reporter: ncohen | Owner: ncohen
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.0
Component: linear programming | Keywords: sd35.5, Cernay2012
Work_issues: | Upstream: N/A
Reviewer: | Author: John Perry
Merged: | Dependencies:
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Comment(by john_perry):
Replying to [comment:68 ncohen]:
> When I try these patches and the new spkg 2 errors remain in
coin_backend.pyx. The first one is not important (a variable n that
represents a string has been declared as a C integer, it is fixed in a
split second)...
Can you tell me which one?
>...and the other is in the copy() function. It looks like the "copied"
object is empty (zero constraints, and p.solve() returns 0, ...). Do you
know where this could come from ? `O_o`
Since Cbc becomes the default solver when you install coin, I recently
noticed that after copying and trying to change the objective function,
Sage would crash, hard. In fact, I was thinking of that this morning
before I came down to the computer.
I am not sure what is going on. I know it '''used''' to work some time
ago, since as you know I had been very interested in making Cbc work at
one point. I'm planning to look at it again, though since GLPK is now
working I was busy working on my research instead. Just this week I've
arrived at a point on the problem I was studying that I think I can look
at this again, so I will try to fix it.
> Oh, and also : why do you want to cache all the values of the variables
in a dictionnary attached to the CoinBackend object ?
If I want to add a constraint after solving once, the Cbc model crashes,
hard. I don't remember if it crashes when I add to the model, or when I
try to solve. The solution I had found, and which worked at ''one'' point,
was to delete the model, but since OsiClp stores the solution in the model
(no joke) you lose the solutions. My solution was to store the values of
the variables; I don't remember how, but a dictionary doesn't sound too
wrong...
Do you think I should store them in C floats? Do you have a better
suggestion?
> It would be nice to see this patch merged in Sage 5.0. Anyway thanks for
all the work you did on this ticket `:-)`
I know. I'll try to work on it, but I have no guarantees that I'll have a
patch soon.
john
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12220#comment:69>
Sage <http://www.sagemath.org>
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