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Treat infeasible and cutoff nodes in the same way #2162

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Treat infeasible and cutoff nodes in the same way #2162

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3373f3c
treat infeasible and cutoff nodes in the same way and set the node lo…
nguidotti Oct 15, 2026
6bc53ee
correctly set the node lower bound in determinism mode
nguidotti Oct 15, 2026
1de09ea
Merge branch 'main' into infeasible-node
nguidotti Oct 15, 2026
63f7d40
Merge branch 'main' into infeasible-node
nguidotti Oct 21, 2026
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20 changes: 9 additions & 11 deletions cpp/src/branch_and_bound/branch_and_bound.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1212,7 +1212,6 @@ struct deterministic_bfs_policy_t
branch_direction_t dir) override
{
switch (status) {
case node_status_t::INFEASIBLE: this->worker.record_infeasible(node); break;
case node_status_t::FATHOMED: this->worker.record_fathomed(node, node->lower_bound); break;
case node_status_t::INTEGER_FEASIBLE:
this->worker.record_integer_solution(node, node->lower_bound);
Expand Down Expand Up @@ -1384,15 +1383,14 @@ std::pair<node_status_t, branch_direction_t> branch_and_bound_t<i_t, f_t>::updat
worker->recompute_bounds = true;

if (lp_status == dual_status_t::DUAL_UNBOUNDED) {
node_ptr->lower_bound = inf;
policy.graphviz(search_tree, node_ptr, "infeasible", 0.0);
search_tree.update(node_ptr, node_status_t::INFEASIBLE);
status = node_status_t::INFEASIBLE;
node_ptr->lower_bound = upper_bound;
policy.graphviz(search_tree, node_ptr, "infeasible", upper_bound);
search_tree.update(node_ptr, node_status_t::FATHOMED);
status = node_status_t::FATHOMED;

} else if (lp_status == dual_status_t::CUTOFF) {
f_t leaf_obj = compute_objective(leaf_problem, leaf_solution.x);
node_ptr->lower_bound = upper_bound;
policy.graphviz(search_tree, node_ptr, "cut off", leaf_obj);
policy.graphviz(search_tree, node_ptr, "cut off", upper_bound);
search_tree.update(node_ptr, node_status_t::FATHOMED);
status = node_status_t::FATHOMED;

Expand Down Expand Up @@ -5274,13 +5272,13 @@ node_status_t branch_and_bound_t<i_t, f_t>::solve_node_deterministic(
#endif

if (!feasible) {
node_ptr->lower_bound = std::numeric_limits<f_t>::infinity();
search_tree.update(node_ptr, node_status_t::INFEASIBLE);
worker.record_infeasible(node_ptr);
node_ptr->lower_bound = worker.local_upper_bound;
search_tree.update(node_ptr, node_status_t::FATHOMED);
worker.record_fathomed(node_ptr, worker.local_upper_bound);
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--exploration_stats_.nodes_unexplored;
++exploration_stats_.nodes_explored;
worker.recompute_bounds_and_basis = true;
return node_status_t::INFEASIBLE;
return node_status_t::FATHOMED;
}

// Solve LP relaxation
Expand Down
9 changes: 0 additions & 9 deletions cpp/src/branch_and_bound/deterministic_workers.hpp
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Expand Up @@ -262,15 +262,6 @@ class deterministic_bfs_worker_t
++total_nodes_pruned;
}

void record_infeasible(mip_node_t<i_t, f_t>* node)
{
record_event(
bb_event_t<i_t, f_t>::make_infeasible(this->clock, this->worker_id, node->creation_seq));
++nodes_processed_this_horizon;
++this->total_nodes_processed;
++total_nodes_infeasible;
}

void record_numerical(mip_node_t<i_t, f_t>* node)
{
record_event(
Expand Down
9 changes: 4 additions & 5 deletions cpp/src/branch_and_bound/mip_node.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -26,16 +26,15 @@ namespace cuopt::mathematical_optimization::mip {
enum class node_status_t : int {
PENDING = 0, // Node is still in the tree, waiting to be solved
INTEGER_FEASIBLE = 1, // Node has an integer feasible solution
INFEASIBLE = 2, // Node is infeasible
FATHOMED = 3, // Node objective is greater than the upper bound
HAS_CHILDREN = 4, // Node has children to explore
NUMERICAL = 5 // Encountered numerical issue when solving the LP relaxation
FATHOMED = 2, // Node is infeasible or has objective is greater than the upper bound
HAS_CHILDREN = 3, // Node has children to explore
NUMERICAL = 4 // Encountered numerical issue when solving the LP relaxation
};

inline bool inactive_status(node_status_t status)
{
return (status == node_status_t::FATHOMED || status == node_status_t::INTEGER_FEASIBLE ||
status == node_status_t::INFEASIBLE || status == node_status_t::NUMERICAL);
status == node_status_t::NUMERICAL);
}

template <typename i_t, typename f_t>
Expand Down
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