GAMS World Forum

In fact, I want the first display Z.l shows the value "a" and the second display Z.l shows the value of "b". To make it more clear from my post and Gideon's: you can't . I think you missed my line opening the code example: Therefore, your code is actually executed in this way by...

(Using GAMS is overkill for this)

Perhaps
is what you are missing ?

GAMS makes two different "passes" of the file when "preparing" the model, they are usually referred to as "compile" and "execution" phase or time. "compile" comes first, then "execution". As you can see in https://www.gams.com/latest/docs/U...

The issue may not be so simple, look at this post by the great Michael Bussieck: https://forum.gamsworld.org/viewtopic.php?t=10080#p23097 But, as far as I understand, no, "Execution" in this context means GAMS execution, not the solver. From the page I linked: This is the time required for...

Hi, why did you discard your first hypothesis ? If you look at the .lst file, you can see that the time is in fact spent in GAMS "execution" and "generation", rather than in the actual "solve" time (which is detailed as "resource use" of each solve. Check: htt...

First. Read https://www.gams.com/products/simple-example/ , you've got all your sum() operators syntax wrong. (this is your 148) Second. In equation cograde, it is written for every " i ". So, when you mean sum( (i,j), ... ) do you really mean " i " again, or do you mean sum(j,.....

I don't know VRP models and sincerely I can't understand from your description what this constraint is supposed to achieve. Do you mean: "If a vehicle arrives at a point p, it must also leave it" ? If so, this can be written as: arrAndDep(k,p).. sum(i$(not sameas(i,p)),x(i,p,k)) =e= sum(i$...

Hmm, this line is incorrect:

arrive(k).. sum((i,pp),x(i,pp,k)) - sum((p,j)$(p.val=pp.val),x(p,j,k))=e=0;

You don't have "control" of set pp at that point, more informally, which element of pp do you mean to appear ?

What is the constraint supposed to achieve ?

What do you think of this intrinsic function ?

signPower(x,Y)

It will get you the value of the real branch when it exists (which is your case).

Is this a MILP model ? Which solver are you using ?