Compress duplicate and singular state label columns

src/pg/PGArena.cc

@@ -235,6 +235,51 @@ int PGArena::computeStateLabels(std::vector<node_id_t>& visited_map, std::vector
         }
     }
 
+    std::cout << "Using " << product_state_size << " components" << std::endl;
+    // identify singular and duplicate columns
+    std::vector<bool> used(product_state_size, true);
+    for (size_t i = 0; i < product_state_size; i++) {
+        if (visited_states[i].size() == 1) {
+            std::cout << "Column " << i << " singular" << std::endl;
+            used[i] = false;
+            continue;
+        }
+        for (size_t j = 0; j < i; j++) {
+            bool column_equal = true;
+            for (node_id_t n = 0; n < n_env_nodes; n++) {
+                if (visited_map[i] != NODE_NONE) {
+                    if (product_states[n][i] != product_states[n][j]) {
+                        column_equal = false;
+                        break;
+                    }
+                }
+            }
+            if (column_equal) {
+                std::cout << "Column " << i << " duplicate of " << j << std::endl;
+                used[i] = false;
+                break;
+            }
+        }
+    }
+
+    // compress states
+    size_t k = 0;
+    for (size_t j = 0; j < product_state_size; j++) {
+        if (used[j]) {
+            if (j != k) {
+                for (node_id_t i = 0; i < n_env_nodes; i++) {
+                    if (visited_map[i] != NODE_NONE) {
+                        product_states[i][k] = product_states[i][j];
+                    }
+                }
+                visited_states[k] = std::move(visited_states[j]);
+                inner_state_map[k] = std::move(inner_state_map[j]);
+            }
+            k++;
+        }
+    }
+    product_state_size = k;
+
     accumulated_bits.resize(product_state_size + 1);
     // get number of bits
     int state_label_bits = 0;
@@ -247,6 +292,7 @@ int PGArena::computeStateLabels(std::vector<node_id_t>& visited_map, std::vector
     }
     accumulated_bits[product_state_size] = state_label_bits;
     constexpr int node_id_t_bitwidth = std::numeric_limits<node_id_t>::digits + std::numeric_limits<node_id_t>::is_signed;
+    std::cout << "Using " << product_state_size << " components with a total of " << state_label_bits << " bits" << std::endl;
     if (state_label_bits > node_id_t_bitwidth) {
         return -1;
     }