[SCIP] / / LPRoot and Original Problem /

[Deleplanque Samuel]

Dear SCIP team,

I'm working on a typical pricing problem. I've two formulations: one is
solved with a Branch & Price and the other one with a typical Branch &
Bound, both using SCIP.
I have a problem with collecting the LP Root for the second one. Indeed, I
would like the LP-Relaxation objective value of my problem and not the
transformed one, or any other solution obtained in the root node.

For example, in the trace bellow, the LP-Relaxation objective value for an
instance of my formulation is 1.041834e+04 (the MIP optimal is found before
any branching).

 time | node  | left  |LP iter|LP it/n| mem |mdpt |frac |vars |cons |cols
|rows |cuts |confs|strbr|  dualbound   | primalbound  |  gap
T 0.0s|     1 |     0 |     0 |     - | 248k|   0 |   - |  10 |  20 |  10 |
 20 |   0 |   0 |   0 |      --      | 0.000000e+00 |    Inf
  0.0s|     1 |     0 |    13 |     - | 246k|   0 |   2 |  10 |  20 |  10 |
 20 |   0 |   0 |   0 | 1.041834e+04 | 0.000000e+00 |    Inf
s 0.0s|     1 |     0 |    13 |     - | 247k|   0 |   2 |  10 |  20 |  10 |
 20 |   0 |   0 |   0 | 1.041834e+04 | 3.029395e+03 | 243.91%
  0.0s|     1 |     0 |    16 |     - | 248k|   0 |   0 |  10 |  20 |  10 |
 21 |   1 |   0 |   0 | 9.957000e+03 | 3.029395e+03 | 228.68%
* 0.0s|     1 |     0 |    16 |     - | 248k|   0 |   - |  10 |  20 |  10 |
 21 |   1 |   0 |   0 | 9.957000e+03 | 9.957000e+03 |   0.00%

If I use any function to obtain the LPRoot value (*SCIPgetLPRootObjval*,
*SCIPgetLPRootObjval* or *SCIPgetLowerboundRoot*) I logically get
9.957000e+03. If I use *SCIPgetSolOrigObj* I obtain the same and not the
1.041834e+04 of the LP relaxation of my original problem.

Also, because I want to compare the two formulations, and then to compare
what is comparable, I would like to know what are the different algorithms
executed in the root. If I try to understand: the T and s mean two
heuristics has been used and * means normally an integral LP-relaxation
(but not for my original problem).

Thanks :)

Samuel Deleplanque

-- 
/***************************************
Samuel Deleplanque, PHD
*PostDoc at Université Libre de Bruxelles*
*Phone:* +32 (0) 2 650 5628, *Fax:* +32 (0) 2 650 5970
*Office:* 2.N3.206 - Building NO, Campus de la Plaine
Boulevard du Triomphe CP 210 / 01
B-1050 *Brussels*, *Belgium                           **Website
<http://sites.google.com/site/samueldeleplanque/>*
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