#9911: Changing the LP formulation of feedback vertex/arc set to improve the
speed
----------------------------+-----------------------------------------------
Reporter: ncohen | Owner: jason, ncohen, rlm
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-4.6.1
Component: graph theory | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
----------------------------+-----------------------------------------------
Changes (by ncohen):
* status: needs_info => needs_review
Comment:
Hello !!!
You are totally right about these lists.. That's just how I coded LP at
first, but it wasn't a good idea after all. You will find the "modern LP
code" easier to read `:-D`
About the formulations... Well, the first one was just the one I came up
with when I first wanted to solve MFAS problems, and the other one was
given to me by a friend who was reading glpk's examples. You will find
this file there :
http://stuff.mit.edu/afs/athena/software/glpk/examples/mfasp.mod
Note that even though the speed improvement is great, I wrote #9923 some
time later and wondered whether I should remove this patch because of it :
there is no comparison possible between this LP formulation and #9923,
which will be (when it will be merged) the default way to solve MFAS
problems. This formulation will just stay as a backup, or to check both
algorithms' correctness (unless people do not want it of course, but
that's what I had in mind when writing #9923)...
(patch updated)
Nathann
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9911#comment:6>
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