[Dip] Differences between GAP examples

[Florian Fontan]

Indeed! I didn't think to look there.

I managed to compile the GAP example. I tested on instance a05100. This 
instance is solved optimally by a naive implementation in CBC in 0.005s. 
The optimal value is 1698 which is actually also the upper bound from 
the linear relaxation. When I try the GAP implementation given as 
example in Dip on this instance (./decomp_gap --param gap.parm)

  * with doPriceCut = 1, doCut = 0, doDirect = 0: the lower bound found
    is 1556, no feasible solution is found and the algorithm doesn't
    terminate after at least several minutes
  * with doPriceCut = 0, doCut = 1, doDirect = 0 or doDirect = 1: the
    algorithm terminates very quickly, returning a best lower bound and
    a best upper bound of 1693. I think it may be the solution of the
    problem with the capacity constraints removed.

Is this the expected behavior?

Florian

Le 11/06/2019 à 22:34, Matthew Galati a écrit :
> The Makefile gives some hints... one case using the built-in MILP 
> solver, one case uses a KP solver.
>
> 	#PC: oracle for KP solve is Pisinger, BranchEnforceInMaster
> 	OBJS += GAP_DecompApp. at OBJEXT@
> 	CFLAGS = -DVERSION1
> 	
> 	#TODO: BranchEnforceInSubProb using GAP_DecompApp2 or by option
> 	
> 	# CPM/PC: built-in MILP solver, dense model build
> 	# BranchEnforceInMaster or BranchEnforceInSubProb by option
> 	#OBJS += GAP_DecompApp3. at OBJEXT@
> 	#CFLAGS += -DVERSION3
> 	
> 	# CPM/PC: built-in MILP solver, sparse model build
> 	# BranchEnforceInMaster or BranchEnforceInSubProb by option
> 	#OBJS += GAP_DecompApp4. at OBJEXT@
> 	#CFLAGS += -DVERSION4
>
>
> On Tue, Jun 11, 2019 at 3:41 PM Florian Fontan <dev at florian-fontan.fr 
> <mailto:dev at florian-fontan.fr>> wrote:
>
>     Dear Dip community,
>
>     I am trying to get familiar with Dip and understand how it works.
>     Could
>     someone tell me the differences between the multiple DecompApp
>     implementation examples for the Generalized Assignment Problem?
>     https://github.com/coin-or/Dip/tree/master/Dip/examples/GAP
>
>     For example, in GAP_DecompApp.cpp, I noticed that the
>     setModelRelax call
>     passes NULL as first argument:
>
>          setModelRelax(NULL, modelName, i);
>
>     whereas in GAP_DecompApp3.cpp, an other model is defined:
>
>          status = createModelPartKP(modelRelax, i);
>          modelName = "KP" + UtilIntToStr(i);
>          setModelRelax(modelRelax, modelName, i);
>
>     What does that mean? I haven't found any documentation about it
>
>     Florian
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