Optimization problem

Hi! I have to maximize an expression that is the sum of many sub-expressions (in the code they are called espressione ) that have some constraints like even their variables contained in the vector var[].

When i try to run the code i have this error:

Solution count 0

Model is infeasible or unbounded

But if i print GRB.OPTIMAL it is 2!. And if i try to do:

fob.computeIIS()
fob.write("model.ilp")

after optimize() my model, i recieve:

Computing Irreducible Inconsistent Subsystem (IIS)...

without having a solution

Here the code:

d=0
var=[]
k=1
indice=0
s=0
vincoli=[]
n=[]
vettore_finale=[]

fob=Model()
fob.params.NonConvex=2
for h in range (0,int(matrice1[i][j])-1):
if h==0:
vettore_somma=[]
for x in range (0,int(matrice1[i][j])-1):

   var.append(fob.addVar(vtype='C',name=str(matrice3[i][j][17][x])))
   vincoli.append(fob.addConstr(var[x+indice]<=vmax)
   vincoli.append(fob.addConstr(var[x+indice]>=vmin))
   var.append(fob.addVar(vtype='C',name=str(matrice3[i][j][18][x])))
   vincoli.append(fob.addConstr(var[x+1+indice]<=sigmamax))
   vincoli.append(fob.addConstr(var[x+1+indice]-sigma<=(sigmamax)))
   vincoli.append(fob.addConstr(-var[x+1+indice]+sigma<=(sigmamax)))
   var.append(fob.addVar(vtype='C',name=str(matrice3[i][j][19][x])))
   vincoli.append(fob.addConstr(var[x+2+indice]==var[x+indice]*var[x+indice]))
   vincoli.append(fob.addConstr(((var[x+2+indice]+e-2*var[x+indice]*e)/matrice6[i][j][0][4][x+1][0])<=imax)

   indice=indice+2

fob.update()
if h==0:
l=len(var)
o=0
u=0
if int(matrice1[i][j])>=3 and h==0:
for x in range (1,l-3,3):

for y in range (x,l-3,3):
vincoli.append(fob.addConstr((var[x]-var[y+3])<=sigmamax))
vincoli.append(fob.addConstr((-var[x]+var[y+3])<=sigmamax))
var.append(fob.addVar(vtype='C',name=str(matrice3[i][j][20][o])))
o=o+1
dim=len(var)
fob.update()

u=0
for y in range (x+1,l-3,3): #vincoli sulle vij^2
vincoli.append(fob.addConstr(var[l+u]==var[x-1]*var[y+1]) )
vincoli.append(fob.addConstr(((var[x+1]+var[y+3]-2*var[l+u])/matrice6[i][j][0][4][x][u+2])<=imax))
u=u+1
print(x)
fob.update()


sin=fob.addVar(vtype='C',name='sin'+str(var[(d+1)])+str(sigma))#sini0
if h!=0 and matrice1[i][j]>=3:
for g in range(0,len(n)):
a=str((var[d+1]))
    b=str(n[g])
    if ((a[13])) in b:
vettore_somma.append(n[g])
q=fob.addVar(vtype='C',name=str(var[(d+1)])+str(sigma))
vincoli.append(fob.addConstr(q==var[d+1]-sigma))
cos=fob.addVar(vtype='C',name='cos'+str(var[(d+1)])+str(sigma))
fob.update()
vincoli.append(fob.addGenConstrSin(q,sin,name='sin'+str(var[d+1])+str(sigma)))
vincoli.append(fob.addGenConstrCos(q,cos,name='cos'+str(var[d+1])+str(sigma)))
fob.update()

u=(var[d+2])*matrice6[i][j][0][8][k][k]
vettore_somma.append(u)
u=(var[d])*e*(matrice6[i][j][0][8][k][0]*cos+matrice6[i][j][0][9][k][0]*sin)
vettore_somma.append(u)

p=0

f=int(matrice1[i][j])-1-k

for y in range (s+l,l+f+s):
if p!=0:
n1=3*p
else:
n1=4*p


sin1=fob.addVar(vtype='C',name='sin'+str(var[(d+1)])+str(var[(d+4+n1)])) q1=fob.addVar(vtype='C',name=str(var[(d+1)])+str(var[(d+4+n1)]))
vincoli.append(fob.addConstr(q1==var[d+1]-var[d+4+n1]))
cos1=fob.addVar(vtype='C',name='cos'+str(var[(d+1)])+str(var[(d+4+n1)]))
fob.update()
                                   vincoli.append(fob.addGenConstrSin(q1,sin1,name='sin'+str(var[d+1])+str(var[d+4+n1])))
vincoli.append(fob.addGenConstrCos(q1,cos1,name='cos'+str(var[d+1])+str(var[d+4+n1])))
fob.update()
u=(var[y])*(matrice6[i][j][0][8][k][p+k+1]*(cos1)+matrice6[i][j][0][9][k][p+k+1]*(sin1))
vettore_somma.append(u)


sin2=fob.addVar(vtype='C',name='sin'+str(var[d+4+n1])+str(var[(d+1)]))
q2=fob.addVar(vtype='C',name=str(var[d+4+n1])+str(var[d+1]))
vincoli.append(fob.addConstr(q2==-var[d+1]+var[d+4+n1]))
cos2=fob.addVar(vtype='C',name='cos'+str(var[(d+4+n1)])+str(var[(d+1)]))
fob.update()
vincoli.append(fob.addGenConstrSin(q2,sin2,name='sin'+str(var[d+4+n1])+str(var[d+1])))
vincoli.append(fob.addGenConstrCos(q2,cos2,name='cos'+str(var[d+4+n1])+str(var[d+1])))
fob.update()
n.append((var[y])*(matrice6[i][j][0][8][k][p+k+1]*cos2+matrice6[i][j][0][9][k][p+k+1]*sin2))
p=p+1

espressione=0
for z in range (0,len(vettore_somma)):
espressione=espressione+vettore_somma[z]
vettore_finale.append(espressione)
print(espressione)
if ass_er==1:
fob.addConstr(espressione<=matrice2[i][j][h+1][17]/Prif)

fob.addConstr(espressione>=(matrice2[i][j][h+1][4]*matrice2[i][j][h+1][9]/(Prif*100)))
d=d+3
k=k+1
s=p
vettore_somma=[]

fob.setObjective(quicksum(vettore_finale[i] for i in range (0,len(vettore_finale))))
fob.update()
fob.optimize()
print(var)
print(vettore_finale)
print (GRB.OPTIMAL)
fob.computeIIS()
fob.write("model.ilp")

正式なコメント

Simranjit Kaur

Gurobi Staff

2025年11月16日 23:42

This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum, or try Gurobot, our chatbot interface offering instant, expert-level support.

Jaromił Najman

2022年02月28日 13:03

Hi Alessandra,

But if i print GRB.OPTIMAL it is 2!

You are printing the value of the enumerator GRB.OPTIMAL which indeed is 2. If you want to know the model's status, you have to

print(fob.status)

Could you try following the KB article How do I resolve the error "Model infeasible or unbounded"?

Best regards,
Jaromił

Optimization problem

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