# Tobias Achterberg

Gurobi Staff
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## Activity overview

Latest activity by Tobias Achterberg
• Tobias Achterberg commented,

This is a delicate issue. We only promise that we will be able to detect the following two cases as convex: 1. x^T Q x <= d with PSD matrix Q2. sum xj² - y² <= 0 with y >= 0 But Gurobi will also be...

• Tobias Achterberg commented,

• Tobias Achterberg commented,

In your formulation, I think that you always need to use (1 - bi) for all the big-M constraints as you have formulated them.

• Tobias Achterberg commented,

I think that your big-M constraints are wrong. For example, b1=0 will force I[v][i] <= 120*SOC_avg[v][i] due to the first big-M constraint. This is not what you want. You only want to force constra...

• Tobias Achterberg commented,

For example, say you have four different regions based on the relationship of x and y in which you have different objective functions. Then you need four binary variables to indicate in which regio...

• Tobias Achterberg commented,

The log file looks okay. It seems pretty difficult to find a feasible solution for your model. What you see in the table is the output of the branch-and-bound tree search. The algorithm successivel...

• Tobias Achterberg commented,

This is actually not a bug. It is due to the large (actually, infinite) domains of your variables and the consequences that this has for the piece-wise linear approximation that we use for the log ...

• Tobias Achterberg commented,

This looks like a bug. Thanks for reporting! I will investigate and check what is going on. Tobias

• Tobias Achterberg commented,

Yes, you can do this manually. But you can also just use the "and" general constraint: addConstr(z == and_(x,y)). Moreover, you can just stick with your quadratic objective function as indicated in...

• Tobias Achterberg commented,

In very rare cases it may even help to also use barrier for the local node relaxations. There is of course the very big downside that barrier cannot benefit from the warm start information that you...