Handle infinity entries correctly when normalize a cost matrix.
[libfirm] / heuristical.c
index c320764..75eee76 100644 (file)
 
 static pbqp_edge **edge_bucket;
 static pbqp_node **node_buckets[4];
+static pbqp_node **reduced_bucket = NULL;
+static int         buckets_filled = 0;
+
+static void insert_into_edge_bucket(pbqp_edge *edge)
+{
+       unsigned bucket_len = ARR_LEN(edge_bucket);
+
+       if (edge->bucket_index < bucket_len && edge_bucket[edge->bucket_index]
+                       == edge)
+               /* Edge is already inserted. */
+               return;
+
+       edge->bucket_index = bucket_len;
+       ARR_APP1(pbqp_edge *, edge_bucket, edge);
+}
 
 static void init_buckets(void)
 {
        int i;
 
        edge_bucket = NEW_ARR_F(pbqp_edge *, 0);
+       reduced_bucket = NEW_ARR_F(pbqp_node *, 0);
 
        for (i = 0; i < 4; ++i) {
                node_buckets[i] = NEW_ARR_F(pbqp_node *, 0);
        }
 }
 
+static void free_buckets(void)
+{
+       int i;
+
+       for (i = 0; i < 4; ++i) {
+               DEL_ARR_F(node_buckets[i]);
+               node_buckets[i] = NULL;
+       }
+
+       DEL_ARR_F(edge_bucket);
+       edge_bucket = NULL;
+
+       DEL_ARR_F(reduced_bucket);
+       reduced_bucket = NULL;
+
+       buckets_filled = 0;
+}
+
 static void fill_node_buckets(pbqp *pbqp)
 {
        unsigned node_index;
@@ -51,6 +85,8 @@ static void fill_node_buckets(pbqp *pbqp)
 
                ARR_APP1(pbqp_node *, node_buckets[arity], node);
        }
+
+       buckets_filled = 1;
 }
 
 static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
@@ -67,8 +103,8 @@ static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
        assert(pbqp);
        assert(edge);
 
-       src_node = get_node(pbqp, edge->src);
-       tgt_node = get_node(pbqp, edge->tgt);
+       src_node = edge->src;
+       tgt_node = edge->tgt;
        assert(src_node);
        assert(tgt_node);
 
@@ -90,10 +126,17 @@ static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
                num min = pbqp_matrix_get_row_min(mat, src_index, tgt_vec);
 
                if (min != 0) {
-                       pbqp_matrix_sub_row_value(mat, src_index, tgt_vec, min);
-                       vector_add_value(src_vec, min);
-
-                       // TODO add to edge_list if inf
+                       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) {
+                               insert_into_edge_bucket(edge);
+                       }
                }
        }
 }
@@ -112,8 +155,8 @@ static void normalize_towards_target(pbqp *pbqp, pbqp_edge *edge)
        assert(pbqp);
        assert(edge);
 
-       src_node = get_node(pbqp, edge->src);
-       tgt_node = get_node(pbqp, edge->tgt);
+       src_node = edge->src;
+       tgt_node = edge->tgt;
        assert(src_node);
        assert(tgt_node);
 
@@ -134,14 +177,68 @@ static void normalize_towards_target(pbqp *pbqp, pbqp_edge *edge)
                num min = pbqp_matrix_get_col_min(mat, tgt_index, src_vec);
 
                if (min != 0) {
-                       pbqp_matrix_sub_col_value(mat, tgt_index, src_vec, min);
-                       vector_add_value(tgt_vec, min);
-
-                       // TODO add to edge_list if inf
+                       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) {
+                               insert_into_edge_bucket(edge);
+                       }
                }
        }
 }
 
+static void reorder_node(pbqp_node *node)
+{
+       unsigned    arity;
+       unsigned    old_arity;
+       unsigned    old_bucket_len;
+       unsigned    old_bucket_index;
+       pbqp_node **old_bucket;
+       pbqp_node  *other;
+
+       if (!buckets_filled) return;
+
+       assert(node);
+
+       arity = ARR_LEN(node->edges);
+
+       /* Same bucket as before */
+       if (arity > 2) return;
+
+       /* Assume node lost one incident edge. */
+       old_arity        = arity + 1;
+       old_bucket       = node_buckets[old_arity];
+       old_bucket_len   = ARR_LEN(old_bucket);
+       old_bucket_index = node->bucket_index;
+
+       if (old_bucket_len <= old_bucket_index || old_bucket[old_bucket_index]
+                       != node) {
+               unsigned bucket_len = ARR_LEN(node_buckets[arity]);
+
+               /* Old arity is new arity, so we have nothing to do. */
+               assert(old_bucket_index < bucket_len);
+               assert(node_buckets[arity][old_bucket_index] == node);
+               return;
+       }
+
+       assert(old_bucket[old_bucket_index] == node);
+
+       /* Delete node from old bucket... */
+       other                        = old_bucket[old_bucket_len - 1];
+       other->bucket_index          = old_bucket_index;
+       old_bucket[old_bucket_index] = other;
+       ARR_SHRINKLEN(node_buckets[old_arity], old_bucket_len - 1);
+
+       /* ..and add to new one. */
+       node->bucket_index = ARR_LEN(node_buckets[arity]);
+       ARR_APP1(pbqp_node*, node_buckets[arity], node);
+}
+
 static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
 {
        pbqp_matrix    *mat;
@@ -155,17 +252,21 @@ static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
        assert(pbqp);
        assert(edge);
 
-       if(pbqp->dump_file) {
+       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", edge->src, edge->tgt);
+               sprintf(txt, "Simplification of Edge n%d-n%d", src_node->index, tgt_node->index);
                dump_section(pbqp->dump_file, 3, txt);
        }
 
-       src_node = get_node(pbqp, edge->src);
-       tgt_node = get_node(pbqp, edge->tgt);
-       assert(src_node);
-       assert(tgt_node);
-
        src_vec = src_node->costs;
        tgt_vec = tgt_node->costs;
        assert(src_vec);
@@ -194,46 +295,13 @@ static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
 
        if (pbqp_matrix_is_zero(mat, src_vec, tgt_vec)) {
                if (pbqp->dump_file) {
-                       fputs("edge has been eliminated", pbqp->dump_file);
-
-                       delete_edge(pbqp, edge);
+                       fputs("edge has been eliminated<br>\n", pbqp->dump_file);
                }
-       }
-}
 
-static void reorder_node(pbqp_node *node)
-{
-       unsigned arity;
-       unsigned old_arity;
-       unsigned old_bucket_len;
-
-       assert(node);
-
-       arity = ARR_LEN(node->edges);
-
-       /* Equal bucket as before */
-       if (arity > 2) return;
-
-       /* Assume node lost one incident edge. */
-       old_arity = arity + 1;
-
-       if (ARR_LEN(node_buckets[old_arity]) <= (int)node->bucket_index
-                       || node_buckets[old_arity][node->bucket_index] != node) {
-               /* Old arity is new arity, so we have nothing to do. */
-               return;
+               delete_edge(edge);
+               reorder_node(src_node);
+               reorder_node(tgt_node);
        }
-
-       old_bucket_len = ARR_LEN(node_buckets[old_arity]);
-       assert (node_buckets[old_arity][node->bucket_index] == node);
-
-       /* Delete node from old bucket... */
-       node_buckets[old_arity][node->bucket_index]
-                       = node_buckets[old_arity][old_bucket_len - 1];
-       ARR_SHRINKLEN(node_buckets[old_arity], (int)old_bucket_len - 1);
-
-       /* ..and add to new one. */
-       node->bucket_index = ARR_LEN(node_buckets[arity]);
-       ARR_APP1(pbqp_node *, node_buckets[arity], node);
 }
 
 void solve_pbqp_heuristical(pbqp *pbqp)
@@ -268,7 +336,7 @@ void solve_pbqp_heuristical(pbqp *pbqp)
                        pbqp_edge *edge = edges[edge_index];
 
                        /* Simplify only once per edge. */
-                       if (node_index != edge->src) continue;
+                       if (node != edge->src) continue;
 
                        simplify_edge(pbqp, edge);
                }
@@ -279,67 +347,455 @@ void solve_pbqp_heuristical(pbqp *pbqp)
 
        for (;;) {
                if (ARR_LEN(edge_bucket) > 0) {
-                       panic("Please implement edge simplification");
+                       apply_edge(pbqp);
                } else if (ARR_LEN(node_buckets[1]) > 0) {
-                       applyRI(pbqp);
+                       apply_RI(pbqp);
                } else if (ARR_LEN(node_buckets[2]) > 0) {
-                       panic("Please implement RII simplification");
+                       apply_RII(pbqp);
                } else if (ARR_LEN(node_buckets[3]) > 0) {
-                       panic("Please implement RN simplification");
+                       apply_RN(pbqp);
                } else {
-                       panic("Please implement back propagation");
-                       // break;
+                       break;
+               }
+       }
+
+       if (pbqp->dump_file) {
+               dump_section(pbqp->dump_file, 1, "4. Determine Solution/Minimum");
+               dump_section(pbqp->dump_file, 2, "4.1. Trivial Solution");
+       }
+
+       /* Solve trivial nodes and calculate solution. */
+       node_len = ARR_LEN(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);
+               pbqp->solution = pbqp_add(pbqp->solution,
+                               node->costs->entries[node->solution].data);
+               if (pbqp->dump_file) {
+                       fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
+                       dump_node(pbqp, node);
+               }
+       }
+
+       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:
+                               back_propagate_RII(pbqp, node);
+                               break;
+                       default:
+                               panic("Only nodes with degree one or two should be in this bucket");
+                               break;
                }
        }
+
+       free_buckets();
+}
+
+void apply_edge(pbqp *pbqp)
+{
+       unsigned   bucket_len = ARR_LEN(edge_bucket);
+       pbqp_edge *edge       = edge_bucket[bucket_len - 1];
+
+       ARR_SHRINKLEN(edge_bucket, (int)bucket_len - 1);
+
+       simplify_edge(pbqp, edge);
 }
 
-void applyRI(pbqp *pbqp)
+void apply_RI(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     = get_node(pbqp, edge->src) == node;
-       unsigned my_index;
-       unsigned other_index;
+       int          is_src     = edge->src == node;
+       pbqp_node   *other_node;
 
        if (is_src) {
-               my_index    = edge->src;
-               other_index = edge->tgt;
+               other_node = edge->tgt;
        } else {
-               my_index    = edge->tgt;
-               other_index = edge->src;
+               other_node = edge->src;
        }
 
        if (pbqp->dump_file) {
                char     txt[100];
-               sprintf(txt, "RI-Reduktion of Node n%d", my_index);
+               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, my_index);
-               dump_node(pbqp, other_index);
+               dump_node(pbqp, node);
+               dump_node(pbqp, other_node);
                dump_edge(pbqp, edge);
        }
 
        if (is_src) {
-               pbqp_node *tgt_node = get_node(pbqp, edge->tgt);
                pbqp_matrix_add_to_all_cols(mat, node->costs);
                normalize_towards_target(pbqp, edge);
-               disconnect_edge(tgt_node, edge);
        } else {
-               pbqp_node *src_node = get_node(pbqp, edge->src);
                pbqp_matrix_add_to_all_rows(mat, node->costs);
                normalize_towards_source(pbqp, edge);
-               disconnect_edge(src_node, edge);
        }
+       disconnect_edge(other_node, edge);
 
        if (pbqp->dump_file) {
                fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
-               dump_node(pbqp, other_index);
+               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 apply_RII(pbqp *pbqp)
+{
+       pbqp_node  **bucket     = node_buckets[2];
+       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;
+
+       assert(pbqp);
+
+       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, src_node);
+               dump_edge(pbqp, src_edge);
+               dump_node(pbqp, node);
+               dump_edge(pbqp, tgt_edge);
+               dump_node(pbqp, 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);
+
+       /* Remove node from bucket... */
        ARR_SHRINKLEN(bucket, (int)bucket_len - 1);
-       reorder_node(get_node(pbqp, other_index));
+
+       /* ...and add it to back propagation list. */
+       node->bucket_index = ARR_LEN(reduced_bucket);
+       ARR_APP1(pbqp_node *, 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, edge);
+       }
+
+       /* Edge has changed so we simplify it. */
+       simplify_edge(pbqp, edge);
+}
+
+void apply_RN(pbqp *pbqp)
+{
+       pbqp_node  **bucket     = node_buckets[3];
+       unsigned     bucket_len = ARR_LEN(bucket);
+       pbqp_node   *node       = bucket[bucket_len - 1];
+       pbqp_edge   *edge;
+       vector      *node_vec   = node->costs;
+       vector      *vec;
+       pbqp_matrix *mat;
+       unsigned     edge_index;
+       unsigned     edge_len   = ARR_LEN(node->edges);
+       unsigned     node_index;
+       unsigned     node_len   = node_vec->len;
+       unsigned     min_index  = 0;
+       num          min        = INF_COSTS;
+       int          is_src;
+
+       assert(pbqp);
+
+       if (pbqp->dump_file) {
+               char     txt[100];
+               sprintf(txt, "RN-Reduction of Node n%d", node->index);
+               dump_section(pbqp->dump_file, 2, txt);
+               pbqp_dump_graph(pbqp);
+       }
+
+       for (node_index = 0; node_index < node_len; ++node_index) {
+               num value = 0;
+
+               for (edge_index = 0; edge_index < edge_len; ++edge_index) {
+                       edge   = node->edges[edge_index];
+                       mat    = edge->costs;
+                       is_src = edge->src == node;
+
+                       if (is_src) {
+                               vec = vector_copy(pbqp, edge->tgt->costs);
+                               vector_add_matrix_row(vec, mat, node_index);
+                       } else {
+                               vec = vector_copy(pbqp, edge->src->costs);
+                               vector_add_matrix_col(vec, mat, node_index);
+                       }
+
+                       value = pbqp_add(value, vector_get_min(vec));
+
+                       obstack_free(&pbqp->obstack, vec);
+               }
+
+               if (value < min) {
+                       min = value;
+                       min_index = node_index;
+               }
+       }
+
+       if (pbqp->dump_file) {
+               fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
+                                       node->index, min_index);
+               fprintf(pbqp->dump_file, "Minimal cost of RN reduction: %d<br>\n",
+                                                       min);
+       }
+
+       node->solution = min_index;
+
+       /* Now that we found the local minimum set all other costs to infinity. */
+       for (node_index = 0; node_index < node_len; ++node_index) {
+               if (node_index != min_index) {
+                       node_vec->entries[node_index].data = INF_COSTS;
+               }
+       }
+
+       /* Add all incident edges to edge bucket, since they are now independent. */
+       for (edge_index = 0; edge_index < edge_len; ++edge_index) {
+               insert_into_edge_bucket(node->edges[edge_index]);
+       }
+}
+
+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);
+       }
+}
+
+void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
+{
+       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;
+       vector      *vec;
+       vector      *node_vec;
+       unsigned     col_index;
+       unsigned     row_index;
+
+       assert(pbqp);
+
+       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;
+
+       node_vec = node->costs;
+
+       row_index = src_node->solution;
+       col_index = tgt_node->solution;
+
+       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);
+       }
+
+       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);
+       }
+
+       obstack_free(&pbqp->obstack, vec);
+}
+
+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;
 }