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Jan 24, 2022 at 6:32 comment added stats_noob Let us continue this discussion in chat.
Jan 23, 2022 at 20:09 comment added prubin I'm moving this to a chat session. You should get the invitation from Stack Exchange.
Jan 23, 2022 at 19:45 comment added stats_noob @ prubin: thank you for your reply! sorry to ask so many questions - if you have time, could you please help me understand this? In the case of the Travelling Salesman Problem - how could we take the "gradient of the objection function"? This seems impossible, no? Could you please expand on this? I can not thank you enough for your help! Thanks!
Jan 23, 2022 at 19:42 comment added prubin No, the objective function will have a gradient. The issue with discrete variables is not whether the objective function has a gradient but to what extent that gradient is meaningful/useful, since "small" changes to the variables do not make sense.
Jan 23, 2022 at 17:12 comment added stats_noob Thank you for your reply! "Most commonly, you will use binary variables xij" - in this case, the objective function will not have a gradient, correct?
Jan 23, 2022 at 17:10 vote accept stats_noob
Jan 23, 2022 at 17:00 comment added prubin The TSP objective function depends on how you define your variables. Most commonly, you will use binary variables $x_{ij}$, taking value 1 if $i\rightarrow j$ is part of the tour. The objective function is linear in the $x_{ij}$ variables, and linear functions have (constant) gradients.
Jan 23, 2022 at 16:32 comment added stats_noob I would have thought that for all discrete combinatorial optimization problems, the objective function will not have a gradient?
Jan 23, 2022 at 16:25 comment added stats_noob thank you for your answer! Just to clarify: the objective function for tsp has no gradient? Thank you so much!
Jan 23, 2022 at 16:20 history answered prubin CC BY-SA 4.0