-static pbqp_edge **edge_bucket;
-static pbqp_node **node_buckets[4];
-static pbqp_node **reduced_bucket = NULL;
-static int buckets_filled = 0;
-
-/* Forward declarations. */
-static void apply_Brute_Force(pbqp *pbqp);
-
-static void insert_into_edge_bucket(pbqp_edge *edge)
-{
- if (edge_bucket_contains(edge_bucket, edge)) {
- /* Edge is already inserted. */
- return;
- }
-
- edge_bucket_insert(&edge_bucket, edge);
-}
-
-static void init_buckets(void)
-{
- int i;
-
- edge_bucket_init(&edge_bucket);
- node_bucket_init(&reduced_bucket);
-
- for (i = 0; i < 4; ++i) {
- node_bucket_init(&node_buckets[i]);
- }
-}
-
-static void free_buckets(void)
-{
- int i;
-
- for (i = 0; i < 4; ++i) {
- node_bucket_free(&node_buckets[i]);
- }
-
- edge_bucket_free(&edge_bucket);
- node_bucket_free(&reduced_bucket);
-
- buckets_filled = 0;
-}
-
-static void fill_node_buckets(pbqp *pbqp)
-{
- unsigned node_index;
- unsigned node_len;
-
- assert(pbqp);
- node_len = pbqp->num_nodes;
-
- for (node_index = 0; node_index < node_len; ++node_index) {
- unsigned degree;
- pbqp_node *node = get_node(pbqp, node_index);
-
- if (!node) continue;
-
- degree = pbqp_node_get_degree(node);
-
- /* We have only one bucket for nodes with arity >= 3. */
- if (degree > 3) {
- degree = 3;
- }
-
- node_bucket_insert(&node_buckets[degree], node);
- }
-
- buckets_filled = 1;
-}
-
-static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
-{
- pbqp_matrix *mat;
- pbqp_node *src_node;
- pbqp_node *tgt_node;
- vector *src_vec;
- vector *tgt_vec;
- int src_len;
- int tgt_len;
- int src_index;
-
- assert(pbqp);
- assert(edge);
-
- src_node = edge->src;
- tgt_node = edge->tgt;
- assert(src_node);
- assert(tgt_node);
-
- src_vec = src_node->costs;
- tgt_vec = tgt_node->costs;
- assert(src_vec);
- assert(tgt_vec);
-
- src_len = src_vec->len;
- tgt_len = tgt_vec->len;
- assert(src_len > 0);
- assert(tgt_len > 0);
-
- mat = edge->costs;
- assert(mat);
-
- /* Normalize towards source node. */
- for (src_index = 0; src_index < src_len; ++src_index) {
- num min = pbqp_matrix_get_row_min(mat, src_index, tgt_vec);
-
- if (min != 0) {
- if (src_vec->entries[src_index].data == INF_COSTS) {
- pbqp_matrix_set_row_value(mat, src_index, 0);
- } else {
- pbqp_matrix_sub_row_value(mat, src_index, tgt_vec, min);
- }
- src_vec->entries[src_index].data = pbqp_add(
- src_vec->entries[src_index].data, min);
-
- if (min == INF_COSTS) {
- unsigned edge_index;
- unsigned edge_len = pbqp_node_get_degree(src_node);
-
- for (edge_index = 0; edge_index < edge_len; ++edge_index) {
- pbqp_edge *edge_candidate = src_node->edges[edge_index];
- if (edge_candidate != edge) {
- insert_into_edge_bucket(edge_candidate);
- }
- }
- }
- }
- }
-}
-
-static void normalize_towards_target(pbqp *pbqp, pbqp_edge *edge)
-{
- pbqp_matrix *mat;
- pbqp_node *src_node;
- pbqp_node *tgt_node;
- vector *src_vec;
- vector *tgt_vec;
- int src_len;
- int tgt_len;
- int tgt_index;
-
- assert(pbqp);
- assert(edge);
-
- src_node = edge->src;
- tgt_node = edge->tgt;
- assert(src_node);
- assert(tgt_node);
-
- src_vec = src_node->costs;
- tgt_vec = tgt_node->costs;
- assert(src_vec);
- assert(tgt_vec);
-
- src_len = src_vec->len;
- tgt_len = tgt_vec->len;
- assert(src_len > 0);
- assert(tgt_len > 0);
-
- mat = edge->costs;
- assert(mat);
-
- for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
- num min = pbqp_matrix_get_col_min(mat, tgt_index, src_vec);
-
- if (min != 0) {
- if (tgt_vec->entries[tgt_index].data == INF_COSTS) {
- pbqp_matrix_set_col_value(mat, tgt_index, 0);
- } else {
- pbqp_matrix_sub_col_value(mat, tgt_index, src_vec, min);
- }
- tgt_vec->entries[tgt_index].data = pbqp_add(
- tgt_vec->entries[tgt_index].data, min);
-
- if (min == INF_COSTS) {
- unsigned edge_index;
- unsigned edge_len = pbqp_node_get_degree(tgt_node);
-
- for (edge_index = 0; edge_index < edge_len; ++edge_index) {
- pbqp_edge *edge_candidate = tgt_node->edges[edge_index];
- if (edge_candidate != edge) {
- insert_into_edge_bucket(edge_candidate);
- }
- }
- }
- }
- }
-}
-
-static void reorder_node(pbqp_node *node)
-{
- unsigned degree = pbqp_node_get_degree(node);
- /* Assume node lost one incident edge. */
- unsigned old_degree = degree + 1;
-
- if (!buckets_filled) return;
-
- /* Same bucket as before */
- if (degree > 2) return;
-
- if (!node_bucket_contains(node_buckets[old_degree], node)) {
- /* Old arity is new arity, so we have nothing to do. */
- assert(node_bucket_contains(node_buckets[degree], node));
- return;
- }
-
- /* Delete node from old bucket... */
- node_bucket_remove(&node_buckets[old_degree], node);
-
- /* ..and add to new one. */
- node_bucket_insert(&node_buckets[degree], node);
-}
-
-static void check_melting_possibility(pbqp *pbqp, pbqp_edge *edge)
-{
- pbqp_matrix *mat;
- pbqp_node *src_node;
- pbqp_node *tgt_node;
- vector *src_vec;
- vector *tgt_vec;
- int src_len;
- int tgt_len;
- int src_index;
- int tgt_index;
-
- assert(pbqp);
- assert(edge);
-
- src_node = edge->src;
- tgt_node = edge->tgt;
- assert(src_node);
- assert(tgt_node);
-
- src_vec = src_node->costs;
- tgt_vec = tgt_node->costs;
- assert(src_vec);
- assert(tgt_vec);
-
- src_len = src_vec->len;
- tgt_len = tgt_vec->len;
- assert(src_len > 0);
- assert(tgt_len > 0);
-
- mat = edge->costs;
- assert(mat);
-
- if (src_len == 1 && tgt_len == 1) {
- //panic("Something is wrong");
- }
-
- int allRowsOk = 1;
- for (src_index = 0; src_index < src_len; ++src_index) {
- int onlyOneZero = 0;
- if (src_vec->entries[src_index].data == INF_COSTS) {
- continue;
- }
- for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
- if (tgt_vec->entries[tgt_index].data == INF_COSTS) {
- continue;
- }
- if (mat->entries[src_index * tgt_len + tgt_index] == 0) {
- if (onlyOneZero) {
- onlyOneZero = 0;
- break;
- } else {
- onlyOneZero = 1;
- continue;
- }
- }
- if (mat->entries[src_index * tgt_len + tgt_index] == INF_COSTS) {
- continue;
- }
- onlyOneZero = 0;
- break;
- }
- allRowsOk &= onlyOneZero;
- }
-
- int allColsOk = 1;
- for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
- int onlyOneZero = 0;
- if (tgt_vec->entries[tgt_index].data == INF_COSTS) {
- continue;
- }
- for (src_index = 0; src_index < src_len; ++src_index) {
- if (src_vec->entries[src_index].data == INF_COSTS) {
- continue;
- }
- if (mat->entries[src_index * tgt_len + tgt_index] == 0) {
- if (onlyOneZero) {
- onlyOneZero = 0;
- break;
- } else {
- onlyOneZero = 1;
- continue;
- }
- }
- if (mat->entries[src_index * tgt_len + tgt_index] == INF_COSTS) {
- continue;
- }
- onlyOneZero = 0;
- break;
- }
- allColsOk &= onlyOneZero;
- }
-
- if (allRowsOk && allColsOk) {
- panic("Hurray");
- }
-}
-
-static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
-{
- pbqp_matrix *mat;
- pbqp_node *src_node;
- pbqp_node *tgt_node;
- vector *src_vec;
- vector *tgt_vec;
- int src_len;
- int tgt_len;
-
- assert(pbqp);
- assert(edge);
-
- src_node = edge->src;
- tgt_node = edge->tgt;
- assert(src_node);
- assert(tgt_node);
-
- /* If edge are already deleted, we have nothing to do. */
- if (!is_connected(src_node, edge) || !is_connected(tgt_node, edge))
- return;
-
- if (pbqp->dump_file) {
- char txt[100];
- sprintf(txt, "Simplification of Edge n%d-n%d", src_node->index, tgt_node->index);
- dump_section(pbqp->dump_file, 3, txt);
- }
-
- src_vec = src_node->costs;
- tgt_vec = tgt_node->costs;
- assert(src_vec);
- assert(tgt_vec);
-
- src_len = src_vec->len;
- tgt_len = tgt_vec->len;
- assert(src_len > 0);
- assert(tgt_len > 0);
-
- mat = edge->costs;
- assert(mat);
-
- if (pbqp->dump_file) {
- fputs("Input:<br>\n", pbqp->dump_file);
- dump_simplifyedge(pbqp, edge);
- }
-
- normalize_towards_source(pbqp, edge);
- normalize_towards_target(pbqp, edge);
-
- if (pbqp->dump_file) {
- fputs("<br>\nOutput:<br>\n", pbqp->dump_file);
- dump_simplifyedge(pbqp, edge);
- }
-
- if (pbqp_matrix_is_zero(mat, src_vec, tgt_vec)) {
- if (pbqp->dump_file) {
- fputs("edge has been eliminated<br>\n", pbqp->dump_file);
- }
-
- delete_edge(edge);
- reorder_node(src_node);
- reorder_node(tgt_node);
- } else {
- //check_melting_possibility(pbqp, edge);
- }
-}
-
-static void initial_simplify_edges(pbqp *pbqp)
-{
- unsigned node_index;
- unsigned node_len;
-
- assert(pbqp);
-
- if (pbqp->dump_file) {
- pbqp_dump_input(pbqp);
- dump_section(pbqp->dump_file, 1, "2. Simplification of Cost Matrices");
- }
-
- node_len = pbqp->num_nodes;
-
- init_buckets();
-
- /* First simplify all edges. */
- for (node_index = 0; node_index < node_len; ++node_index) {
- unsigned edge_index;
- pbqp_node *node = get_node(pbqp, node_index);
- pbqp_edge **edges;
- unsigned edge_len;
-
- if (!node) continue;
-
- edges = node->edges;
- edge_len = pbqp_node_get_degree(node);
-
- for (edge_index = 0; edge_index < edge_len; ++edge_index) {
- pbqp_edge *edge = edges[edge_index];
-
- /* Simplify only once per edge. */
- if (node != edge->src) continue;
-
- simplify_edge(pbqp, edge);
- }
- }
-}
-
-num determine_solution(FILE *file)
-{
- unsigned node_index;
- unsigned node_len;
- num solution;
-
- if (file) {
- dump_section(file, 1, "4. Determine Solution/Minimum");
- dump_section(file, 2, "4.1. Trivial Solution");
- }
-
- /* Solve trivial nodes and calculate solution. */
- node_len = node_bucket_get_length(node_buckets[0]);
- for (node_index = 0; node_index < node_len; ++node_index) {
- pbqp_node *node = node_buckets[0][node_index];
- assert(node);
-
- node->solution = vector_get_min_index(node->costs);
- solution = pbqp_add(solution,
- node->costs->entries[node->solution].data);
- if (file) {
- fprintf(file, "node n%d is set to %d<br>\n", node->index, node->solution);
- dump_node(file, node);
- }
- }
-
- if (file) {
- dump_section(file, 2, "Minimum");
- fprintf(file, "Minimum is equal to %lld.", solution);
- }
-
- return solution;
-}
-
-static void back_propagate(pbqp *pbqp)
-{
- unsigned node_index;
- unsigned node_len = node_bucket_get_length(reduced_bucket);
-
- assert(pbqp);
- if (pbqp->dump_file) {
- dump_section(pbqp->dump_file, 2, "Back Propagation");
- }
-
- for (node_index = node_len; node_index > 0; --node_index) {
- pbqp_node *node = reduced_bucket[node_index - 1];
-
- switch (pbqp_node_get_degree(node)) {
- case 1:
- back_propagate_RI(pbqp, node);
- break;
- case 2:
- back_propagate_RII(pbqp, node);
- break;
- default:
- panic("Only nodes with degree one or two should be in this bucket");
- break;
- }
- }
-}
-
-static void apply_heuristic_reductions(pbqp *pbqp)
-{
- for (;;) {
- if (edge_bucket_get_length(edge_bucket) > 0) {
- apply_edge(pbqp);
- } else if (node_bucket_get_length(node_buckets[1]) > 0) {
- apply_RI(pbqp);
- } else if (node_bucket_get_length(node_buckets[2]) > 0) {
- apply_RII(pbqp);
- } else if (node_bucket_get_length(node_buckets[3]) > 0) {
- apply_RN(pbqp);
- } else {
- return;
- }
- }
-}
-
-void solve_pbqp_heuristical(pbqp *pbqp)
-{
- /* Reduce nodes degree ... */
- initial_simplify_edges(pbqp);
-
- /* ... and put node into bucket representing their degree. */
- fill_node_buckets(pbqp);
-
- apply_heuristic_reductions(pbqp);
-
- pbqp->solution = determine_solution(pbqp->dump_file);
-
- /* Solve reduced nodes. */
- back_propagate(pbqp);
-
- free_buckets();
-}
-
-void apply_edge(pbqp *pbqp)
-{
- pbqp_edge *edge = edge_bucket_pop(&edge_bucket);
-
- simplify_edge(pbqp, edge);
-}
-
-void apply_RI(pbqp *pbqp)
-{
- pbqp_node *node = node_bucket_pop(&node_buckets[1]);
- pbqp_edge *edge = node->edges[0];
- pbqp_matrix *mat = edge->costs;
- int is_src = edge->src == node;
- pbqp_node *other_node;
-
- assert(pbqp_node_get_degree(node) == 1);
-
- if (is_src) {
- other_node = edge->tgt;
- } else {
- other_node = edge->src;
- }
-
- if (pbqp->dump_file) {
- char txt[100];
- sprintf(txt, "RI-Reduction of Node n%d", node->index);
- dump_section(pbqp->dump_file, 2, txt);
- pbqp_dump_graph(pbqp);
- fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
- dump_node(pbqp->dump_file, node);
- dump_node(pbqp->dump_file, other_node);
- dump_edge(pbqp->dump_file, edge);
- }
-
- if (is_src) {
- pbqp_matrix_add_to_all_cols(mat, node->costs);
- normalize_towards_target(pbqp, edge);
- } else {
- pbqp_matrix_add_to_all_rows(mat, node->costs);
- normalize_towards_source(pbqp, edge);
- }
- disconnect_edge(other_node, edge);
-
- if (pbqp->dump_file) {
- fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
- dump_node(pbqp->dump_file, other_node);
- }
-
- reorder_node(other_node);
-
- /* Add node to back propagation list. */
- node_bucket_insert(&reduced_bucket, node);
-}
-
-void apply_RII(pbqp *pbqp)
-{
- pbqp_node *node = node_bucket_pop(&node_buckets[2]);
- pbqp_edge *src_edge = node->edges[0];
- pbqp_edge *tgt_edge = node->edges[1];
- int src_is_src = src_edge->src == node;
- int tgt_is_src = tgt_edge->src == node;
- pbqp_matrix *src_mat;
- pbqp_matrix *tgt_mat;
- pbqp_node *src_node;
- pbqp_node *tgt_node;
- pbqp_matrix *mat;
- vector *vec;
- vector *node_vec;
- vector *src_vec;
- vector *tgt_vec;
- unsigned col_index;
- unsigned col_len;
- unsigned row_index;
- unsigned row_len;
- unsigned node_len;
-
- assert(pbqp);
- assert(pbqp_node_get_degree(node) == 2);
-
- if (src_is_src) {
- src_node = src_edge->tgt;
- } else {
- src_node = src_edge->src;
- }
-
- if (tgt_is_src) {
- tgt_node = tgt_edge->tgt;
- } else {
- tgt_node = tgt_edge->src;
- }
-
- /* Swap nodes if necessary. */
- if (tgt_node->index < src_node->index) {
- pbqp_node *tmp_node;
- pbqp_edge *tmp_edge;
-
- tmp_node = src_node;
- src_node = tgt_node;
- tgt_node = tmp_node;
-
- tmp_edge = src_edge;
- src_edge = tgt_edge;
- tgt_edge = tmp_edge;
-
- src_is_src = src_edge->src == node;
- tgt_is_src = tgt_edge->src == node;
- }
-
- if (pbqp->dump_file) {
- char txt[100];
- sprintf(txt, "RII-Reduction of Node n%d", node->index);
- dump_section(pbqp->dump_file, 2, txt);
- pbqp_dump_graph(pbqp);
- fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
- dump_node(pbqp->dump_file, src_node);
- dump_edge(pbqp->dump_file, src_edge);
- dump_node(pbqp->dump_file, node);
- dump_edge(pbqp->dump_file, tgt_edge);
- dump_node(pbqp->dump_file, tgt_node);
- }
-
- src_mat = src_edge->costs;
- tgt_mat = tgt_edge->costs;
-
- src_vec = src_node->costs;
- tgt_vec = tgt_node->costs;
- node_vec = node->costs;
-
- row_len = src_vec->len;
- col_len = tgt_vec->len;
- node_len = node_vec->len;
-
- mat = pbqp_matrix_alloc(pbqp, row_len, col_len);
-
- for (row_index = 0; row_index < row_len; ++row_index) {
- for (col_index = 0; col_index < col_len; ++col_index) {
- vec = vector_copy(pbqp, node_vec);
-
- if (src_is_src) {
- vector_add_matrix_col(vec, src_mat, row_index);
- } else {
- vector_add_matrix_row(vec, src_mat, row_index);
- }
-
- if (tgt_is_src) {
- vector_add_matrix_col(vec, tgt_mat, col_index);
- } else {
- vector_add_matrix_row(vec, tgt_mat, col_index);
- }
-
- mat->entries[row_index * col_len + col_index] = vector_get_min(vec);
-
- obstack_free(&pbqp->obstack, vec);
- }
- }
-
- pbqp_edge *edge = get_edge(pbqp, src_node->index, tgt_node->index);
-
- /* Disconnect node. */
- disconnect_edge(src_node, src_edge);
- disconnect_edge(tgt_node, tgt_edge);
-
- /* Add node to back propagation list. */
- node_bucket_insert(&reduced_bucket, node);
-
- if (edge == NULL) {
- edge = alloc_edge(pbqp, src_node->index, tgt_node->index, mat);
- } else {
- pbqp_matrix_add(edge->costs, mat);
-
- /* Free local matrix. */
- obstack_free(&pbqp->obstack, mat);
-
- reorder_node(src_node);
- reorder_node(tgt_node);
- }
-
- if (pbqp->dump_file) {
- fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
- dump_edge(pbqp->dump_file, edge);
- }
-
- /* Edge has changed so we simplify it. */
- simplify_edge(pbqp, edge);
-}