understanding GAMS syntax in a mathematical way

GAMS
1

Hi, as you can read in https://www.gams.com/latest/docs/userguides/mccarl/fx.htm, when doing x1.fx=9 actually:

… GAMS sets the lower and upper bound to that value.

This means x1.fx=9 is exactly doing x1.lo=9 and x1.up=9 in one statement.

Additionaly, this kind of statements (setting variable attributes) are executed in order. So when you do x1.lo=8 afterwards, you are “overwriting” the previous set of the lower bound.

Best regards!
Claudio

2

you mean a constraint defined ? ie

c1… q=l=someValue;

q.up=someValue;

This would lead to models which are identical on the mathematical level, but NOT on the “software” (GAMS+solver) level.