I wrote a relatively simpler model where the acreage will be allocated

between two different crops (Grasses and Stover).

There are no non-linearities involving the acreage terms. Still, I got

this error #56

“56 Endogenous operands for * not allowed in linear models.”

In stead of LP, I used NLP to solve the problem and I was able to

obtain feasible results. But, I was surprised why this would happen -

since I use only a products but without any non-linear operations (no

power ** or Max/Min/ABS functions?

The following are the only two equations, where the vStoverAc(zone,

quarter) and vGrassac(z) appear. Other equations in the model are

based upon the total biomass derived from these acreages.

What other factors should I be careful about to understand such error

message of non-linearity? I seek this because I am planning to

introduce some non-linearity in acreage terms (or a round-about method

of iterative solve command).

eCostFunction… vCumulativeCost =e=

Sum[(z,q), vcost(“Grass”,z,q) * Yield(“Grass”,q) * vGrassAc(z)]

- Sum[(z,q), vcost(“Stover”,z,q) * Yield(“Stover”,q) * vStoverAc(z,q)]
- Sum[(F,q),(D * vStorage(F,q))]
- [Sum(z,vTerminalcost(‘Stover’,z))/Card(z)]* vExcessStover_T
- [Sum(z,vTerminalcost(‘Grass’,z))/Card(z)]*

vExcessGrass_T ;

*Supply of Stover and Grass in quarter q

eGrassSupply(q)… vGrassS(q) =e= Sum(z,Yield(“Grass”,q) *

vGrassAc(z)) ;

eStoverSupply(q)… vStoverS(q) =e= Sum(z,Yield(“Stover”,q) *

vStoverAc(z,q)) ;

Thank you for your reply.

Subbu Kumarappan

–~–~---------~–~----~------------~-------~–~----~

To post to this group, send email to gamsworld@googlegroups.com

To unsubscribe from this group, send email to gamsworld+unsubscribe@googlegroups.com

For more options, visit this group at http://groups.google.com/group/gamsworld?hl=en

-~----------~----~----~----~------~----~------~–~—

\