Here is the running result. I can't get a result or I have get the result. Because I test my model under small network, we can get perfect answer, in which sum_flow1 and sum_flow2 had values not 0. However, when I test the model under larger network, I just get the answer as bellow, in which the sum_flow1 and sum_flow2 always had value 0.
Besides, why does it accur--Presolve: All rows and columns removed?
Because it doesn't appear when I test a small network, but in larger networks.
Gurobi 5.5.0: mipgap = 0.000000000000000000000000000000000000000000000000000000001
outlev = 1
Optimize a model with 2050 rows, 270 columns and 1534 nonzeros
Presolve removed 270 rows and 2050 columns
Presolve time: 0.00s
Presolve: All rows and columns removed
Iteration Objective Primal Inf. Dual Inf. Time
0 9.9086144e-01 0.000000e+00 0.000000e+00 0s
16 9.9086144e-01 0.000000e+00 0.000000e+00 0s
Solved in 16 iterations and 0.00 seconds
Optimal objective 9.908614362e-01
Gurobi 5.5.0: optimal solution; objective 0.9908614362
16 simplex iterations
sum_flow1 [*,*] (tr)
: P2 P4 P5 :=
P2N1 0 . .
P2N2 0 . .
P2N3 0 . .
P2N4 0 . .
P2N5 0 . .
P2N6 0 . .
P2N7 0 . .
P2N8 0 . .
P2N9 0 . .
P4N1 . 0 .
P4N2 . 0 .
P4N3 . 0 .
P4N4 . 0 .
P4N5 . 0 .
P4N6 . 0 .
P4N7 . 0 .
P4N8 . 0 .
P5N1 . . 0
P5N2 . . 0
P5N3 . . 0
P5N4 . . 0
P5N5 . . 0
P5N6 . . 0
P5N7 . . 0
P5N8 . . 0
P5N9 . . 0
;
sum_flow2 [*,*] (tr)
: P2 P4 P5 :=
P2N1 0 . .
P2N2 0 . .
P2N3 0 . .
P2N4 0 . .
P2N5 0 . .
P2N6 0 . .
P2N7 0 . .
P2N8 0 . .
P2N9 0 . .
P4N1 . 0 .
P4N2 . 0 .
P4N3 . 0 .
P4N4 . 0 .
P4N5 . 0 .
P4N6 . 0 .
P4N7 . 0 .
P4N8 . 0 .
P5N1 . . 0
P5N2 . . 0
P5N3 . . 0
P5N4 . . 0
P5N5 . . 0
P5N6 . . 0
P5N7 . . 0
P5N8 . . 0
P5N9 . . 0
;
I need help from all of you .
Thank you.