ABS Function may not work
AnsweredGurobi outputs x=0 and y=1 for the given straightforward model, contrary to the expected values of x=1 and y=0. It appears that the ABS function might be malfunctioning. I seek clarification to determine if this discrepancy stems from ABSrelated issues or a potential misunderstanding in my model formulation. Any insights or comments on this matter would be greatly appreciated.

Minimize
2 x + y
Subject To
diff:  x + y + diff1 = 0
abs_condition: absx >= 1
Bounds
1 <= x <= 3
1 <= y <= 3
Generals
x y
General Constraints
abs_value: absx = ABS ( diff1 )
End

# Objective value = 1
x 0
y 1
diff1 1
absx 1


Hi,
The issue is the lower bound of diff1. By default, variables have a lower bound of 0. Your solution x=1 and y=0 is infeasible since it would require diff1=1. If allow negative values for for diff1, you get the solution you expect.
Silke
0 
Thank you.
I understand.
I can achieve the expected result by adding 'Inf <= diff1 <= Inf'.0
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