✨ Remove dangling PIs and redundant POs during network parsing

include/fiction/algorithms/network_transformation/fanout_substitution.hpp

@@ -54,6 +54,14 @@ struct fanout_substitution_params
      * Maximum number of outputs any gate is allowed to have before substitution applies.
      */
     uint32_t threshold = 1ul;
+    /**
+     * Omit dangling PIs.
+     */
+    bool cleanup_dangling_pis = true;
+    /**
+     * Omit redundant POs, i.e. POs connected to a PI or constant.
+     */
+    bool remove_redundant_pos = true;
 };
 
 namespace detail
@@ -135,6 +143,12 @@ class fanout_substitution_impl
         // restore signal names if applicable
         fiction::restore_names(ntk_topo, substituted, old2new);
 
+        // Remove dangling PIs and POs
+        if (ps.cleanup_dangling_pis || ps.remove_redundant_pos)
+        {
+            substituted = mockturtle::cleanup_dangling(substituted, ps.cleanup_dangling_pis, ps.remove_redundant_pos);
+        }
+
         return substituted;
     }
 

test/algorithms/network_transformation/fanout_substitution.cpp

@@ -115,3 +115,21 @@ TEST_CASE("Consistent fanout substitution after balancing", "[fanout-substitutio
     auto balanced_tec = network_balancing<technology_network>(substituted_tec);
     CHECK(is_fanout_substituted(balanced_tec));
 }
+
+TEST_CASE("Cleanup dangling PIs", "[fanout-substitution]")
+{
+    const auto aig                  = blueprints::maj4_network<mockturtle::aig_network>();
+    const auto aig_with_dangling_pi = blueprints::dangling_pi_network<mockturtle::aig_network>();
+
+    fanout_substitution_params ps_breadth{fanout_substitution_params::substitution_strategy::BREADTH, 3, 1, true, true};
+    const auto substituted_breadth = fanout_substitution<technology_network>(aig_with_dangling_pi, ps_breadth);
+    CHECK(substituted_breadth.size() == (aig.size() + 35));
+    CHECK(is_fanout_substituted(substituted_breadth, ps_breadth));
+    check_eq(aig, substituted_breadth);
+
+    fanout_substitution_params ps_depth{fanout_substitution_params::substitution_strategy::DEPTH, 2, 2, true, true};
+    const auto substituted_depth = fanout_substitution<technology_network>(aig_with_dangling_pi, ps_depth);
+    CHECK(substituted_depth.size() == (aig.size() + 34));
+    CHECK(is_fanout_substituted(substituted_depth, ps_depth));
+    check_eq(aig, substituted_depth);
+}

test/utils/blueprints/network_blueprints.hpp

@@ -358,6 +358,31 @@ mockturtle::names_view<Ntk> topolinano_network()
     return ntk;
 }
 
+template <typename Ntk>
+mockturtle::names_view<Ntk> dangling_pi_network()
+{
+    mockturtle::names_view<Ntk> ntk{};
+
+    const auto a = ntk.create_pi("a");
+    const auto b = ntk.create_pi("b");
+    const auto c = ntk.create_pi("c");
+    const auto d = ntk.create_pi("d");
+    const auto e = ntk.create_pi("e");
+    ntk.create_pi("f");
+
+    const auto m1 = ntk.create_maj(a, b, c);
+    const auto m2 = ntk.create_maj(b, c, d);
+    const auto m3 = ntk.create_maj(c, d, e);
+    const auto m4 = ntk.create_maj(m1, m2, m3);
+
+    ntk.create_po(m1, "m1");
+    ntk.create_po(m2, "m2");
+    ntk.create_po(m3, "m3");
+    ntk.create_po(m4, "m4");
+
+    return ntk;
+}
+
 }  // namespace blueprints
 
 #endif  // FICTION_NETWORK_BLUEPRINTS_HPP