Originally posted by: Sothea

Hi,

I use a mex file developped by my research director to optimise a MIQP problem. After a a few hours of running, i got a message as below:

QPSOLVER: OK changed problem type to CPXPROB_MIQP
QPSOLVER: # of variables: 1752
# of constraints: 4396
# of nonzero elements in constraint matrix: 17302
QPSOLVER: Cplex Version 12.3
QPSOLVER: Initiating QP MIP solution...
??? QPSOLVER: Error occurred during the optimization
Error in ==> gignac_MIQP5 at 857
obj,x=qpmipsolver123ssi('new',1,Q,C,Aind,Aval,sense,b,lb,ub,ctype);
Do you know this issue? thanks in advance,
Sothea
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: Sothea

In fact my problem above related to time step. It concerns Irrigation scheduling. So the variables decisions depend on time step (dt). For example i would like optimise a schedule for one day, i decide dt=1h, so number of time step = 24. For the same problem, i decide dt=15 mn, the number of time step incresse to 96. I would like to show that for the same problem, the variables decision can increase or reduce up on dt.
For the problem above, i use dt too small. But when i increase dt and i execute agrain the problem, i got the result.

QPSOLVER: OK changed problem type to CPXPROB_MIQP
QPSOLVER: # of variables: 312
# of constraints: 766
# of nonzero elements in constraint matrix: 2782
QPSOLVER: Cplex Version 12.3
QPSOLVER: Initiating QP MIP solution...
QPSOLVER: Other problem = 102
X Optimum=
obj=0.32535

I dont understand in the messsage " other problem 102", what does it mean? Does the problem above is caused by number of varaible and contraints which are too big?
To get the result for 312 variables and 766 constraint, running time is about 30 mn (capacity marchine : 2duo CPU P8700 @2.53GHz and memory 2Go). Is it normal? How can we reduce running time?

Thanks in advance for your answering.
Sothea
#CPLEXOptimizers
#DecisionOptimization

Originally posted by: John Cui

Firstly, I think you need to ask the developer of QPSOLVER, if what is "102" mean?

Secondly, we have our MATLAB interface, like cplexmiqp, cplexmilp, Cplex class, and so on. I suggest you try to use our CPLEX build-in MATLAB interface.

John Cui
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#DecisionOptimization

Originally posted by: Sothea

Dear John Cui,

Thanks to your help, i can use matlab interface with cplex. After running of my problem and i would like to ask you somes details. When i view the output, i got the message :

output =

cplexstatus: 102
cplexstatusstring: 'integer optimal, tolerance'
iterations: 89839
algorithm: 12
time: 4.266
message: 'Solution with numerical issues'

1) I would like to know what does it mean "102"? I think it is the same message which i got when i run my problem with our mex file.
2) I would like you explain me also about 'Solution with numerical issues', which problem come from and how i can deal it.
3) I would like to check the relaxation, conflits, error and journal motor as in OPL studio, how can i do?

Thanks in advance,
Sothea
#CPLEXOptimizers
#DecisionOptimization