Dear Members of GAMS world,

I added some slack variables to my code, then I found the problem has no solution. I can get the optimal solution before adding the slacks.

But I cannot tell the difference, and don’t know why this could happen. My code is as below:

eq20(t)… sum(i,E(i,t))+ebd(t)+loe(t)=e=D(t);

eq21… -lp+sum(t,loe(t))/sum(t,D(t))=e=0;

eq22(i,t)(ord(i) lt 3).. -RE(i,t)*P(i)*eta(i)*n(i)+e(i,t)=e=0;
eq23(i,t)(ord(i) eq 3)… -RE(i,t)*P(i)*eta(i)*m(t)+e(i,t)=e=0;

then I change to

eq20(t)… -sum(i,e(i,t))-ebd(t)-loe(t)-slackc(t)=l=D(t);

eq21… -lp+sum(t,loe(t))/sum(t,D(t))-slackd=l=0;

eq22(i,t)(ord(i) lt 3).. -RE(i,t)*P(i)*eta(i)*n(i)+e(i,t)-slacka(i,t)=l=0;
eq23(i,t)(ord(i) eq 3)… -RE(i,t)*eta(i)*m(t)+e(i,t)-slackb(i,t)=l=0;

eq24(i,t)… slacka(i,t)=l=1e-6;

eq25(i,t)… slackb(i,t)=l=1e-6;

eq26(t)… slackc(t)=l=1e-6;

eq27… slackd=l=1e-6;

Can any body tell me why for the second case I can’t get a solution? I added the slacks because I want to convert the equalities into inequalities. If not by adding slacks, is there any other way deal with it correctly?

Thank you.

## Regards,

Tina

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