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Hello everyone,

I am currrently doing a project for my university and  I have this type of error :  CPLEX cannot handle MIQCP models with quadratic equality constraints like 'BtoWCosts_definition(91789)'.

I checked all my variables and my constraints but couldn’t find any “quadritic” ones. 

And the error message tell me the error is in the definition of the variable “BtoWCosts” but again I can changed a lot of thing  and It still didn’t work. 

Here is the definition “ BtoW(W)* (NumberTrucks(W)*Truckload(W) )”

where Btow(w) is binary and the 2 others Intergers…

Thanks You in advance,

Yoyo1

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Best answer by mohansx 6 May 2020, 01:57

@Yoyo1 , only one of BtoW, NumberTrucks and Truckload can be variables for this definition to be accepted as a linear constraint. I am expecting both BtoW and NumberTrucks are variables in your case ?

You will need some constraints like NumberTrucks(W) <= BtoW(W) * SomeBigM and the definition as  NumberTrucks(W) * Truckload(W) which will result in 0 costs if BtoW(W) = 0. 

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@Yoyo1 , only one of BtoW, NumberTrucks and Truckload can be variables for this definition to be accepted as a linear constraint. I am expecting both BtoW and NumberTrucks are variables in your case ?

You will need some constraints like NumberTrucks(W) <= BtoW(W) * SomeBigM and the definition as  NumberTrucks(W) * Truckload(W) which will result in 0 costs if BtoW(W) = 0. 

Thank you @mohansx ,

Indeed they are both variables . I used your method and the quadratic error is gone. 

Now I have this one :

“Postsolve integer variables' is relaxed from 'Round integers and resolve LP' to 'No rounding'.
Warning: Postsolve indicates that solution to MinTotalCost is not reliable.
Warning at line 1 in user-defined function section "MainExecution":

The thing is I already changed the range of all my variables in “free” so I don’t see where is the problem. 

Thanks in advance,

Yoyo1

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