+
+ if (pbqp->dump_file) {
+ dump_section(pbqp->dump_file, 2, "Minimum");
+ fprintf(pbqp->dump_file, "Minimum is equal to %d.", pbqp->solution);
+ dump_section(pbqp->dump_file, 2, "Back Propagation");
+ }
+
+ /* Solve reduced nodes. */
+ node_len = ARR_LEN(reduced_bucket);
+ for (node_index = node_len; node_index > 0; --node_index) {
+ pbqp_node *node = reduced_bucket[node_index - 1];
+ assert(node);
+
+ switch (ARR_LEN(node->edges)) {
+ case 1:
+ back_propagate_RI(pbqp, node);
+ break;
+ case 2:
+ panic("Please implement back propagation for RII");
+ break;
+ default:
+ panic("Only nodes with degree one or two should be in this bucket");
+ break;
+ }
+ }
+}
+
+void applyRI(pbqp *pbqp)
+{
+ pbqp_node **bucket = node_buckets[1];
+ unsigned bucket_len = ARR_LEN(bucket);
+ pbqp_node *node = bucket[bucket_len - 1];
+ pbqp_edge *edge = node->edges[0];
+ pbqp_matrix *mat = edge->costs;
+ int is_src = edge->src == node;
+ pbqp_node *other_node;
+
+ if (is_src) {
+ other_node = edge->tgt;
+ } else {
+ other_node = edge->src;
+ }
+
+ if (pbqp->dump_file) {
+ char txt[100];
+ sprintf(txt, "RI-Reduktion 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, node);
+ dump_node(pbqp, other_node);
+ dump_edge(pbqp, 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, other_node);
+ }
+
+ /* Remove node from bucket... */
+ ARR_SHRINKLEN(bucket, (int)bucket_len - 1);
+ reorder_node(other_node);
+
+ /* ...and add it to back propagation list. */
+ node->bucket_index = ARR_LEN(reduced_bucket);
+ ARR_APP1(pbqp_node *, reduced_bucket, node);
+}
+
+void applyRII(pbqp *pbqp)
+{
+ pbqp_node **bucket = node_buckets[1];
+ unsigned bucket_len = ARR_LEN(bucket);
+ pbqp_node *node = bucket[bucket_len - 1];
+ 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;
+
+ 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;
+ }
+
+ 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 = ARR_LEN(src_vec);
+ col_len = ARR_LEN(tgt_vec);
+ node_len = ARR_LEN(node_vec);
+
+ 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_index(vec);
+ }
+ }
+
+ pbqp_edge *edge = get_edge(pbqp, src_node->index, tgt_node->index);
+
+ 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);
+ }
+
+ /* Disconnect node. */
+ disconnect_edge(src_node, src_edge);
+ disconnect_edge(tgt_node, tgt_edge);
+
+ /* Edge has changed so we simplify it. */
+ simplify_edge(pbqp, edge);
+}
+
+void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
+{
+ pbqp_edge *edge;
+ pbqp_node *other;
+ pbqp_matrix *mat;
+ vector *vec;
+ int is_src;
+
+ assert(pbqp);
+ assert(node);
+
+ edge = node->edges[0];
+ mat = edge->costs;
+ is_src = edge->src == node;
+ vec = node->costs;
+
+ if (is_src) {
+ other = edge->tgt;
+ assert(other);
+ vector_add_matrix_col(vec, mat, other->solution);
+ } else {
+ other = edge->src;
+ assert(other);
+ vector_add_matrix_row(vec, mat, other->solution);
+ }
+
+ node->solution = vector_get_min_index(vec);
+ if (pbqp->dump_file) {
+ fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
+ }
+}
+
+int node_is_reduced(pbqp_node *node)
+{
+ if (!reduced_bucket) return 0;
+
+ assert(node);
+ if (ARR_LEN(node->edges) == 0) return 1;
+
+ unsigned bucket_length = ARR_LEN(reduced_bucket);
+ unsigned bucket_index = node->bucket_index;
+
+ return bucket_index < bucket_length && reduced_bucket[bucket_index] == node;