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2436943794
* Initial plan * Convert postfix to prefix increment in for loops Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com> * Fix member variable increment conversion bug Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com> * Update API generator to produce prefix increments Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com> --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
113 lines
3.1 KiB
C++
113 lines
3.1 KiB
C++
/*++
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Copyright (c) 2020 Microsoft Corporation
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Module Name:
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int_branch.cpp
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Abstract:
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Branch heuristic
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Author:
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Lev Nachmanson (levnach)
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Nikolaj Bjorner (nbjorner)
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Revision History:
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--*/
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#include "math/lp/int_solver.h"
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#include "math/lp/lar_solver.h"
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#include "math/lp/int_branch.h"
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namespace lp {
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int_branch::int_branch(int_solver& lia):lia(lia), lra(lia.lra) {}
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lia_move int_branch::operator()() {
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lra.move_non_basic_columns_to_bounds();
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int j = find_inf_int_base_column();
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return j == -1? lia_move::sat : create_branch_on_column(j);
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}
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lia_move int_branch::create_branch_on_column(int j) {
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TRACE(check_main_int, tout << "branching" << std::endl;);
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lia.get_term().clear();
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SASSERT(j != -1);
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lia.get_term().add_monomial(mpq(1), j);
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if (lia.is_free(j)) {
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lia.is_upper() = lia.settings().random_next() % 2;
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lia.offset() = mpq(0);
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}
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else {
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lia.is_upper() = lia.settings().random_next() % 2;
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lia.offset() = lia.is_upper()? floor(lia.get_value(j)) : ceil(lia.get_value(j));
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}
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TRACE(int_solver,
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lia.display_column(tout << "branching v" << j << " = " << lia.get_value(j) << "\n", j);
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tout << "k = " << lia.offset() << std::endl;);
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return lia_move::branch;
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}
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int int_branch::find_inf_int_base_column() {
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#if 1
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return lia.select_int_infeasible_var();
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#endif
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int result = -1;
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mpq range;
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mpq new_range;
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mpq small_value(1024);
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unsigned n = 0;
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lar_core_solver & lcs = lra.get_core_solver();
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unsigned prev_usage = 0; // to quiet down the compiler
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unsigned k = 0;
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unsigned usage;
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unsigned j;
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// this loop looks for a column with the most usages, but breaks when
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// a column with a small span of bounds is found
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for (; k < lra.r_basis().size(); ++k) {
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j = lra.r_basis()[k];
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if (!lia.column_is_int_inf(j))
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continue;
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usage = lra.usage_in_terms(j);
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if (lia.is_boxed(j) && (range = lcs.m_r_upper_bounds[j].x - lcs.m_r_lower_bounds[j].x - rational(2*usage)) <= small_value) {
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result = j;
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k++;
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n = 1;
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break;
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}
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if (n == 0 || usage > prev_usage) {
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result = j;
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prev_usage = usage;
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n = 1;
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} else if (usage == prev_usage && (lia.settings().random_next() % (++n) == 0)) {
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result = j;
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}
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}
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SASSERT(k == lra.r_basis().size() || n == 1);
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// this loop looks for boxed columns with a small span
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for (; k < lra.r_basis().size(); ++k) {
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j = lra.r_basis()[k];
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if (!lia.column_is_int_inf(j) || !lia.is_boxed(j))
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continue;
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SASSERT(!lia.is_fixed(j));
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usage = lra.usage_in_terms(j);
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new_range = lcs.m_r_upper_bounds[j].x - lcs.m_r_lower_bounds[j].x - rational(2*usage);
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if (new_range < range) {
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n = 1;
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result = j;
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range = new_range;
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} else if (new_range == range && (lia.settings().random_next() % (++n) == 0)) {
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result = j;
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}
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}
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return result;
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}
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}
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