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[BUG] Fixed starting variable bounds for diving #474

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Merged
rapids-bot merged 2 commits into from
Oct 10, 2025
Merged

[BUG] Fixed starting variable bounds for diving #474

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0d8e1de
small refactor based on feedback
nguidotti Oct 10, 2025
d44c802
Merge branch 'branch-25.10' into fix-diving-bounds
nguidotti Oct 10, 2025
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22 changes: 11 additions & 11 deletions cpp/src/dual_simplex/branch_and_bound.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -562,8 +562,8 @@ node_status_t branch_and_bound_t<i_t, f_t>::solve_node(search_tree_t<i_t, f_t>&
{
f_t abs_fathom_tol = settings_.absolute_mip_gap_tol / 10;

std::vector<variable_status_t>& leaf_vstatus = node_ptr->vstatus;
lp_solution_t<i_t, f_t> leaf_solution(leaf_problem.num_rows, leaf_problem.num_cols);
std::vector<variable_status_t>& leaf_vstatus = node_ptr->vstatus;
assert(leaf_vstatus.size() == leaf_problem.num_cols);

std::vector<bool> bounds_changed(leaf_problem.num_cols, false);
Expand All @@ -572,7 +572,6 @@ node_status_t branch_and_bound_t<i_t, f_t>::solve_node(search_tree_t<i_t, f_t>&
// two vectors at each node and potentially cause memory issues
node_ptr->get_variable_bounds(leaf_problem.lower, leaf_problem.upper, bounds_changed);

std::vector<f_t> leaf_edge_norms = edge_norms_; // = node.steepest_edge_norms;
simplex_solver_settings_t lp_settings = settings_;
lp_settings.set_log(false);
lp_settings.cut_off = upper_bound + settings_.dual_tol;
Expand All @@ -587,8 +586,9 @@ node_status_t branch_and_bound_t<i_t, f_t>::solve_node(search_tree_t<i_t, f_t>&
dual::status_t lp_status = dual::status_t::DUAL_UNBOUNDED;

if (feasible) {
i_t node_iter = 0;
f_t lp_start_time = tic();
i_t node_iter = 0;
f_t lp_start_time = tic();
std::vector<f_t> leaf_edge_norms = edge_norms_; // = node.steepest_edge_norms;

lp_status = dual_phase2(2,
0,
Expand Down Expand Up @@ -778,7 +778,7 @@ void branch_and_bound_t<i_t, f_t>::exploration_ramp_up(search_tree_t<i_t, f_t>*
}

template <typename i_t, typename f_t>
void branch_and_bound_t<i_t, f_t>::explore_subtree(i_t id,
void branch_and_bound_t<i_t, f_t>::explore_subtree(i_t task_id,
search_tree_t<i_t, f_t>& search_tree,
mip_node_t<i_t, f_t>* start_node,
lp_problem_t<i_t, f_t>& leaf_problem,
Expand All @@ -788,7 +788,7 @@ void branch_and_bound_t<i_t, f_t>::explore_subtree(i_t id,
stack.push_front(start_node);

while (stack.size() > 0 && status_ == mip_exploration_status_t::RUNNING) {
if (id == 0) { repair_heuristic_solutions(); }
if (task_id == 0) { repair_heuristic_solutions(); }

mip_node_t<i_t, f_t>* node_ptr = stack.front();
stack.pop_front();
Expand All @@ -804,10 +804,10 @@ void branch_and_bound_t<i_t, f_t>::explore_subtree(i_t id,
// - The current node and its siblings uses the lower bound of the parent before solving the LP
// relaxation
// - The lower bound of the parent is lower or equal to its children
assert(id < local_lower_bounds_.size());
local_lower_bounds_[id] = lower_bound;
i_t nodes_explored = (++stats_.nodes_explored);
i_t nodes_unexplored = (--stats_.nodes_unexplored);
assert(task_id < local_lower_bounds_.size());
local_lower_bounds_[task_id] = lower_bound;
i_t nodes_explored = (++stats_.nodes_explored);
i_t nodes_unexplored = (--stats_.nodes_unexplored);
stats_.nodes_since_last_log++;

if (lower_bound > upper_bound || rel_gap < settings_.relative_mip_gap_tol) {
Expand All @@ -818,7 +818,7 @@ void branch_and_bound_t<i_t, f_t>::explore_subtree(i_t id,

f_t now = toc(stats_.start_time);

if (id == 0) {
if (task_id == 0) {
f_t time_since_last_log = stats_.last_log == 0 ? 1.0 : toc(stats_.last_log);

if (((stats_.nodes_since_last_log >= 1000 || abs_gap < 10 * settings_.absolute_mip_gap_tol) &&
Expand Down
2 changes: 1 addition & 1 deletion cpp/src/dual_simplex/branch_and_bound.hpp
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Expand Up @@ -235,7 +235,7 @@ class branch_and_bound_t {
i_t initial_heap_size);

// Explore the search tree using the best-first search with plunging strategy.
void explore_subtree(i_t id,
void explore_subtree(i_t task_id,
search_tree_t<i_t, f_t>& search_tree,
mip_node_t<i_t, f_t>* start_node,
lp_problem_t<i_t, f_t>& leaf_problem,
Expand Down