multiply of 2 variables

GAMS
1

Hello GAMS users,

I am beginer of GAMS.

Recently, I found that the multiply of 2 variables make error.
(variable3 = variable1 * variable2;)

The model is as follows:

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-

$TITLE Test

$OFFSYMXREF
$OFFSYMLIST
$eolcom //

scalars
a /5/
b /10/
;

variables
va_a / lo 0, up 10 /
va_b / lo 0, up 10 /
va_x
;

equations
equ
;

equ… va_x =e= a + b + va_a*va_b;

model m /all/;
option MINLP=SBB;
solve m using MINLP maximizing va_x;

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-

Code’s LST file say to me that result is infeasible.

---- equ =E=

equ… (0)*va_a + (0)*va_b + va_x =E= 15 ; (LHS = 0, INFES = 15 ****)


So, if anyone can tell me how to code the case. Is it really
impossible?
I would really appreciate it.

Thanks a lot,

\

2

Hello
If you are mixed up with the reflected form of equation, I should say that this is the linearized form of your equation. Please refer to this thread that a similar problem is discussed.
http://groups.google.com/group/gamsworld/browse_thread/thread/a04a6dbef8e56717?pli=1

Further more it is always a good idea to provide GAMS with initial guesses for nonlinear problems. Which you can do using “.l” or level. As an example in ur case it would be :
va_a.l=2;
va_b.l=3;
va_x.l= a + b + va_a.l*va_b.l;
I hope it will help

محمد صادق تولّلی
Mohammad Sadegh Tavallali
tavallali.msadegh@gmail.com

On Mon, Dec 20, 2010 at 12:21 PM, Young Ki wrote:


Hello GAMS users,

I am beginer of GAMS.

Recently, I found that the multiply of 2 variables make error.
(variable3 = variable1 * variable2;)

The model is as follows:

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-

$TITLE Test

$OFFSYMXREF
$OFFSYMLIST
$eolcom //

scalars
a /5/
b /10/
;

variables
va_a / lo 0, up 10 /
va_b / lo 0, up 10 /
va_x
;

equations
equ
;

equ… va_x =e= a + b + va_a*va_b;

model m /all/;
option MINLP=SBB;
solve m using MINLP maximizing va_x;

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
=-=-=-=-

Code’s LST file say to me that result is infeasible.

---- equ =E=

equ… (0)*va_a + (0)*va_b + va_x =E= 15 ; (LHS = 0, INFES = 15 ****)


So, if anyone can tell me how to code the case. Is it really
impossible?
I would really appreciate it.

Thanks a lot,

–
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\

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