Re: [Help-glpk] A question on row generation

[Andrew Makhorin]

> When the GLPK does row generation, is it true that at each node of
> the B&B (or B&C) tree a different set of rows may be generated and
> added to the LP relaxation at that node, and all the child nodes of
> that node will inherit the generated rows from their parents?

Yes, it is true. Every child subproblem is exact copy of its parent
having some additional constraints (depending on the branching type).
Note, however, that the callback routine being called at level k (i.e.
if the current subproblem has level k) can change or remove only rows,
which were added on the same level; it must neither remove nor change
rows added on previous levels as well as original rows, which already
exist on entry to glp_intopt. New rows generated by the callback are
added to the end of the row list, so on entry to the callback routine
the current subproblem has the following structure:

   original row           <--- first row
   original row
   ...
   original row
   row added on level 0
   ...
   row added on level 0
   row added on level 1
   ...
   row added on level 1
   ...
   ...
   row added on level k-1
   row added on level k
   ...
   row added on level k   <--- last row