RE: [Help-glpk] NO PRIMAL FEASIBLE SOLUTION

[Meketon, Marc]

Whenever I solve these types of models, I add parallel movement arcs with no upperbound and very high cost.  That way (and it might involve some other artificial arcs and/or nodes) I guarantee feasibililty.

 

If any of these very-high cost arcs have positive flow, then you can usually pinpoint where your problems are.

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From: address@hidden on behalf of Erwin Pritanto
Sent: Mon 10/9/2006 4:01 AM
To: address@hidden
Subject: [Help-glpk] NO PRIMAL FEASIBLE SOLUTION

I develop a movement model which will distribute grain optimally from surplus regions to deficit regions. Some regions will receive in large amounts while others in small amounts. The distribution depends on the harvest periods, stock levels in senders & receivers, demand and the availability & cost of transporters.

 

When I ran the model with glpk, I got comments that the model has no feasible solution:

 

sw: glpsol --model move-4.mod

Reading model section from move-4.mod...

Reading data section from move-4.mod...

move-4.mod:188: warning: final NL missing before end of file

188 lines were read

Generating TotalCost...

Generating BalanceInPeriod_1...

Generating BalanceInPeriod_t...

Generating ShipLimit...

Generating ShortLimit...

Generating NoMove...

Model has been successfully generated

lpx_simplex: original LP has 9049 rows, 8736 columns, 34208 non-zeros

PROBLEM HAS NO PRIMAL FEASIBLE SOLUTION

lpx_integer: optimal solution of LP relaxation required

Time used:   0.0 secs

Memory used: 11.1M (11652795 bytes)

sw:

 

Have somebody suggestions for me? I suspect that mixing the large and small amounts distribution (small and large values in the matrix) may cause the infeasibility.

 

Thank you very much

Erwin

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