How to make the branch and cut tree only use Barrier to solve the node LP？
AnsweredI have a large MILP problem (with 230 k variables, 130k of them are integers, and 100k constraints), I have a way to grouping the variables so that I can get the solution faster than doing nothing. And I know that using barrier is the fastest way to solve the LPs in branch and cut. Then I met the problem, when I set Method=2 and NodeMethod=2, the result is not as I expected. Then I want to find out the details on each B&C nodes, but it seems I cannot get the method used on that node using callback. Can you help me with the forcing Gurobi to use barrier only and get a more detailed log about B&C nodes ?

In addition to setting Method=2 and NodeMethod=2, you also have to set Crossover=0. This avoids the computation of a basis solution at the end of the root node which automatically leads to the usage of the Simplex algorithm for nodes.
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