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[BUG] Fix variable fixing for initial solutions #1580

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Merged
rapids-bot merged 3 commits into from
Jul 16, 2026
+21 −7
Merged

[BUG] Fix variable fixing for initial solutions #1580

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9dfbe3a
fix seeding the initial population before properly handling the free …
nguidotti Jul 16, 2026
c247bfe
removed comments. compare solution before and after PDLP with variabl…
nguidotti Jul 16, 2026
ed45538
Merge branch 'main' into fix-initial-solution
nguidotti Jul 16, 2026
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21 changes: 14 additions & 7 deletions cpp/src/mip_heuristics/diversity/diversity_manager.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -240,6 +240,10 @@ void diversity_manager_t<i_t, f_t>::add_user_given_solutions(
}

if (problem_ptr->pre_process_assignment(init_sol_assignment)) {
raft::copy(sol.assignment.data(),
init_sol_assignment.data(),
init_sol_assignment.size(),
sol.handle_ptr->get_stream());
relaxed_lp_settings_t lp_settings;
lp_settings.time_limit = std::min(60., timer.remaining_time() / 2);
lp_settings.tolerance = problem_ptr->tolerances.absolute_tolerance;
Expand All @@ -250,11 +254,15 @@ void diversity_manager_t<i_t, f_t>::add_user_given_solutions(
problem_ptr->integer_indices,
lp_settings,
static_cast<bound_presolve_t<i_t, f_t>*>(nullptr));
raft::copy(sol.assignment.data(),
init_sol_assignment.data(),
init_sol_assignment.size(),
sol.handle_ptr->get_stream());
bool is_feasible = sol.compute_feasibility();
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if (!is_feasible) {
raft::copy(sol.assignment.data(),
init_sol_assignment.data(),
init_sol_assignment.size(),
sol.handle_ptr->get_stream());
is_feasible = sol.compute_feasibility();
}

cuopt_func_call(sol.test_variable_bounds(true));
CUOPT_LOG_DEBUG("Adding initial solution success! feas %d objective %f excess %f",
is_feasible,
Expand All @@ -264,9 +272,8 @@ void diversity_manager_t<i_t, f_t>::add_user_given_solutions(
initial_sol_vector.emplace_back(std::move(sol));
} else {
CUOPT_LOG_ERROR(
"Error cannot add the provided initial solution! \
Assignment size %lu \
initial solution size %lu",
"Error cannot add the provided initial solution! Assignment size %lu initial solution size "
"%lu",
sol.assignment.size(),
init_sol_assignment.size());
}
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7 changes: 7 additions & 0 deletions cpp/src/mip_heuristics/problem/problem.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -1706,6 +1706,13 @@ void problem_t<i_t, f_t>::fix_given_variables(problem_t<i_t, f_t>& original_prob
variables_to_fix.end(),
[variable_fix_mask = make_span(fixing_helpers.variable_fix_mask)] __device__(
i_t x) { variable_fix_mask[x] = 1; });
cuopt_func_call(thrust::for_each(handle_ptr->get_thrust_policy(),
variables_to_fix.begin(),
variables_to_fix.end(),
[assignment = make_span(assignment)] __device__(i_t x) {
cuopt_assert(isfinite(assignment[x]),
"Fixing a variable to a non-finite value");
}));
const i_t num_segments = original_problem.n_constraints;
f_t initial_value{0.};

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