Tell me

Problems with syntax of GAMS
Post Reply
Ildar
User
User
Posts: 8
Joined: 6 months ago

Tell me

Post by Ildar » 4 months ago

Hello


I want to skip finding a valid solution in CPLEX, go directly to the branch and bound method
Tell me how to set a valid solution for my model.
It is necessary to set the value of the function only or vector solution too?
Suppose I know that for this test problem the value of the function does not exceed 350
Attachments
gams.300.3_1.gms
Test
(2.48 MiB) Downloaded 18 times
gamsLP.gms
Model
(1011 Bytes) Downloaded 14 times

Fred
Posts: 158
Joined: 3 years ago

Re: Tell me

Post by Fred » 4 months ago

Hi,

you cannot go directly to the branch and bound method without solving the root node LP.
If you would like to providea starting point, which is basically a (partial) integer feasible solution, you can do that by setting the level attribute .l of the variables before the solve statemment and instruct CPLEX to use that starting point via option misptart (https://www.gams.com/latest/docs/S_CPLE ... EXmipstart).

For your model, the barrier algorithm seems to work better for the root node LP than Simplex. CPLEX option startalg allows you to choose the MIP starting algorithm, e.g.

Code: Select all

[...]
Shops.optfile = 1;
$onecho > cplex.opt
startalg 4
$offecho
Solve Shops using MIP max opt;
[...]
I hope this helps!

Fred

Post Reply