[Coin-discuss] Using CbcHeuristicFPump outside branch and cut

[John J Forrest]

James,

Using FPump should not slow it down.  When I try it is only used at the
root node with setWhen NOT being used.  This means when_ will be 1 and the
code at line 84 of CbcHeuristicFPump.cpp will return at once unless it is
at root node.

However you should be able to use it outside branchAndBound - I may get
time to look at it.

You are correct about documentation being wrong way round.

John Forrest




                                                                           
             "James Gibbons"                                               
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                                       [Coin-discuss] Using                
                                       CbcHeuristicFPump outside branch    
             04/04/06 09:37 AM         and cut                             
                                                                           
                                                                           
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Hi,

Hopefully this will be my last question for a bit. I've found that using
CbcHeuristicFPump finds a good solution for my problem. Unfortunately, it
then slows down the rest of branchAndBound(). The documentation recommends
using it outside branch and cut, but I can't work out how to do this. My
attempt is at the end of this email. From the source code it looks as if
CbcHeuristicFPump::solution will always return 0 using my code because
model_->getCurrentPassNumber() (line 88 of CbcHeuristicFPump.cpp) will
always be 0. I tried the naive bodge of changing line 90 to if
(!atRoot||passNumber>1) but this caused a crash. Is there a way around
this?

BTW there is a documentation error in CBCHeuristicFPump.hpp, line 36, which
I *think* gets 1 and 0 the wrong way around.

Thanks,
James

My code:

CbcModel model(*solver1);
CbcHeuristicFPump heur0(model);

double heurObjVal(1.0e50);
double *heurSol;
heur4.setWhen(3);
model.addHeuristic(&heur0);

int heurState = model.heuristic(0)->solution(heurObjVal,heurSol);
if(heurState!=0) {
    model.setBestSolution(CBC_HEURISTIC_SOLUTION,heurObjVal,heurSol);
}
model.heuristic(0)->setWhen(0);     //turn it off

model.branchAndBound();


--
Dr James Gibbons
Research Fellow
Division of Agricultural & Environmental Sciences
School of Biosciences
University of Nottingham
Sutton Bonington Campus
Loughborough
LE12 5RD

direct line: 0115 9516081
fax:           0115 9516060
e-mail:       james.gibbons at nottingham.ac.uk

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