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Integrate nseq_parith into nielsen_graph; add k upper bound and check_parikh_conflict

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Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
This commit is contained in:
copilot-swe-agent[bot] 2026-03-11 05:10:30 +00:00
parent 35ee8f917d
commit eca5fcc7bb
4 changed files with 137 additions and 1 deletions
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31
src/smt/seq/seq_nielsen.cpp
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@ -20,6 +20,7 @@ Author:
--*/
#include "smt/seq/seq_nielsen.h"
#include "smt/seq/nseq_parith.h"
#include "ast/arith_decl_plugin.h"
#include "ast/ast_pp.h"
#include "util/hashtable.h"
@ -431,10 +432,12 @@ namespace seq {
nielsen_graph::nielsen_graph(euf::sgraph& sg, simple_solver& solver):
m_sg(sg),
m_solver(solver) {
m_solver(solver),
m_parith(alloc(nseq_parith, sg)) {
}
nielsen_graph::~nielsen_graph() {
dealloc(m_parith);
reset();
}
@ -1032,6 +1035,23 @@ namespace seq {
// nielsen_graph: search
// -----------------------------------------------------------------------
void nielsen_graph::apply_parikh_to_node(nielsen_node& node) {
if (node.m_parikh_applied) return;
node.m_parikh_applied = true;
// Generate modular length constraints (len(str) = min_len + stride·k, etc.)
// and append them to the node's integer constraint list.
m_parith->apply_to_node(node);
// Lightweight feasibility pre-check: does the Parikh modular constraint
// contradict the variable's current integer bounds? If so, mark this
// node as a Parikh-image conflict immediately (avoids a solver call).
if (!node.is_currently_conflict() && m_parith->check_parikh_conflict(node)) {
node.m_is_general_conflict = true;
node.m_reason = backtrack_reason::parikh_image;
}
}
void nielsen_graph::assert_root_constraints_to_solver() {
if (m_root_constraints_asserted) return;
m_root_constraints_asserted = true;
@ -1129,6 +1149,15 @@ namespace seq {
return search_result::sat;
}
// Apply Parikh image filter: generate modular length constraints and
// perform a lightweight feasibility pre-check. The filter is guarded
// internally (m_parikh_applied) so it only runs once per node.
apply_parikh_to_node(*node);
if (node->is_currently_conflict()) {
++m_stats.m_num_simplify_conflict;
return search_result::unsat;
}
// integer feasibility check: collect side constraints along the path
// and verify they are jointly satisfiable using the LP solver
if (!cur_path.empty() && !check_int_feasibility(node, cur_path)) {