Originally posted by: BerkUstun

I am trying to solve a very simple MILP using the CPLEX 12.2 API in MATLAB but running into trouble.

The error I encounter is:

Error using ==> cplexlink122
CPLEX Error 1004: Null pointer for required data.
Error in ==> /home/software/cplex/cplex-12.2/cplex/matlab/@Cplex/Cplex.p>Cplex.solve at 640
% Returns:

Error in ==> /home/software/cplex/cplex-12.2/cplex/matlab/@Cplex/Cplex.p>Cplex.subsref at 2396
640 % Returns:

The MILP I am trying to solve has the following structure

obj: 17x1 double
lb: 17x1 double
ub: 17x1 double
rhs: 18.00
lhs: 1.00
A: http://1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
ctype: 'BBBBBBBBBBBBBBBBB'
Where lb = zeros(17,1) and ub = ones(17,1).

The other fields of the MILP (DisplayFunc, Param) are unchanged. Also, the issue seems to be with CPLEX 12.2 since I can save this LP and solve it on another computer that runs MATLAB with the CPLEX 12.3 API.

Anyone have an idea of what could be going wrong?
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: John Cui

Could you please attach your matlab code here?

John Cui
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: BerkUstun

Hi John,

I ended up figuring out what was going wrong in the process of trying to recreate the error.

The issue was linked to the fact that I was using a struct() to create the Model part of my Cplex object. This was a little bit of a speedup compared to building the LP directly from LP.Model.

In particular the following code will lead to an error in CPLEX 12.2:

Model = struct()
Model.obj = ones(5,1)
Model.A = ones(1,5)
Model.lhs = 1
Model.rhs = Inf
Model.ctype = char()
Model.ub = ones(5,1)
Model.lb = zeros(5,1)
LP = Cplex
LP.Model = Model;

However this will work fine:

LP = Cplex
Model = LP.Model
Model.obj = ones(5,1)
Model.A = ones(1,5)
Model.lhs = 1
Model.rhs = Inf
Model.ctype = char()
Model.ub = ones(5,1)
Model.lb = zeros(5,1)
LP.Model = Model

Thanks as always!
#CPLEXOptimizers
#DecisionOptimization