Thread Subject: linprog

I try solving :
 
min c'x
st. Ax <= b
    Aeqx = beq
    x<=ub

When I using the function 'linprog' ,I got the following information
:

Exiting:One or more of the residuals, duality gap, or total relative
error
has grown 100000 times greater than its minimum value so
far:
the primal appears to be infeasible (and the dual
unbounded).
(The dual residual < TolFun=1.00e-008.)

Can anyone help me to see What the problem is??
How can I resolve this problem?
Thanks a lot.

Hi Vilma,

TOMLAB /CPLEX will tell you exactly what the problem is - potentially
also solve it. The infeasibility finder needs to be activated.

Best wishes, Marcus
Tomlab Optimization Inc.
 <http://tomlab.biz>

Vilma Ramada wrote:
>
>
> I try solving :
>
> min c'x
> st. Ax <= b
> Aeqx = beq
> x<=ub
>
> When I using the function 'linprog' ,I got the following
> information
> :
>
> Exiting:One or more of the residuals, duality gap, or total
> relative
> error
> has grown 100000 times greater than its minimum value so
> far:
> the primal appears to be infeasible (and the dual
> unbounded).
> (The dual residual < TolFun=1.00e-008.)
>
> Can anyone help me to see What the problem is??
> How can I resolve this problem?
> Thanks a lot.

Hi Marcus,

could you tell me how I can activate the infeasibility finder?

Thanx,
Eva

"Marcus M. Edvall" <medvREMall@tomREMlab.biREMz> wrote in message <ef22c0a.0@webx.raydaftYaTP>...
> Hi Vilma,
>
> TOMLAB /CPLEX will tell you exactly what the problem is - potentially
> also solve it. The infeasibility finder needs to be activated.
>
> Best wishes, Marcus
> Tomlab Optimization Inc.
> <http://tomlab.biz>
>
> Vilma Ramada wrote:
> >
> >
> > I try solving :
> >
> > min c'x
> > st. Ax <= b
> > Aeqx = beq
> > x<=ub
> >
> > When I using the function 'linprog' ,I got the following
> > information
> > :
> >
> > Exiting:One or more of the residuals, duality gap, or total
> > relative
> > error
> > has grown 100000 times greater than its minimum value so
> > far:
> > the primal appears to be infeasible (and the dual
> > unbounded).
> > (The dual residual < TolFun=1.00e-008.)
> >
> > Can anyone help me to see What the problem is??
> > How can I resolve this problem?
> > Thanks a lot.

On 13 Mai, 12:05, "Evdokia " <evdoki...@hotmail.com> wrote:
> Hi Marcus,
>
> could you tell me how I can activate the infeasibility finder?
>
> Thanx,
> Eva
>
> "Marcus M. Edvall" <medvREM...@tomREMlab.biREMz> wrote in message <ef22c0...@webx.raydaftYaTP>...
>
>
>
> > Hi Vilma,
>
> > TOMLAB /CPLEX will tell you exactly what the problem is - potentially
> > also solve it. The infeasibility finder needs to be activated.
>
> > Best wishes, Marcus
> > Tomlab Optimization Inc.
> >  <http://tomlab.biz>
>
> > Vilma Ramada wrote:
>
> > > I try solving :
>
> > > min c'x
> > > st. Ax <= b
> > > Aeqx = beq
> > > x<=ub
>
> > > When I using the function 'linprog' ,I got the following
> > > information
> > > :
>
> > > Exiting:One or more of the residuals, duality gap, or total
> > > relative
> > > error
> > > has grown 100000 times greater than its minimum value so
> > > far:
> > > the primal appears to be infeasible (and the dual
> > > unbounded).
> > > (The dual residual < TolFun=1.00e-008.)
>
> > > Can anyone help me to see What the problem is??
> > > How can I resolve this problem?
> > > Thanks a lot.- Zitierten Text ausblenden -
>
> - Zitierten Text anzeigen -

You want to activate the infeasibility finder in CPLEX ? Because MATAB
does not have this feature ...

Best wishes
Torsten.

"Vilma Ramada" <vilma.cristina.ramada@marinha.pt> wrote in message <ef22c0a.-1@webx.raydaftYaTP>...
> I try solving :
>
> min c'x
> st. Ax <= b
> Aeqx = beq
> x<=ub
=================

MATLAB thinks there exists no x satisfying your constraints. The easiest thing would be if you already know at least one x that is supposed to be feasible. You could then test the constraints Ax*b, etc... to see which one isn't satisfied as it should be.

Hi Vilma,
Here are two suggestions:
* Increase TolFun to 1e-6 and rerun.
* Try primal simplex algorithm, i.e.
 X =
linprog(f,A,b,Aeq,beq,LB,UB,X0,optimset('LargeScale','off','Simplex','on')).

Do these give you a better outcome. If you still have problems, you could
send me your problem and I can have a look.

Regards,
Derya


"Evdokia " <evdokia02@hotmail.com> wrote in message
news:iqivoh$h0t$1@newscl01ah.mathworks.com...
> Hi Marcus,
>
> could you tell me how I can activate the infeasibility finder?
>
> Thanx,
> Eva
>
> "Marcus M. Edvall" <medvREMall@tomREMlab.biREMz> wrote in message
> <ef22c0a.0@webx.raydaftYaTP>...
>> Hi Vilma,
>>
>> TOMLAB /CPLEX will tell you exactly what the problem is - potentially
>> also solve it. The infeasibility finder needs to be activated.
>>
>> Best wishes, Marcus
>> Tomlab Optimization Inc.
>> <http://tomlab.biz>
>>
>> Vilma Ramada wrote:
>> >
>> >
>> > I try solving :
>> >
>> > min c'x
>> > st. Ax <= b
>> > Aeqx = beq
>> > x<=ub
>> >
>> > When I using the function 'linprog' ,I got the following
>> > information
>> > :
>> >
>> > Exiting:One or more of the residuals, duality gap, or total
>> > relative
>> > error
>> > has grown 100000 times greater than its minimum value so
>> > far:
>> > the primal appears to be infeasible (and the dual
>> > unbounded).
>> > (The dual residual < TolFun=1.00e-008.)
>> >
>> > Can anyone help me to see What the problem is??
>> > How can I resolve this problem?
>> > Thanks a lot.