Vector names are const.
[libfirm] / heuristical.c
index fcbb70f..98e7c4b 100644 (file)
@@ -4,7 +4,9 @@
 
 #include "bucket.h"
 #include "heuristical.h"
+#if    KAPS_DUMP
 #include "html_dumper.h"
+#endif
 #include "kaps.h"
 #include "matrix.h"
 #include "pbqp_edge.h"
@@ -18,28 +20,32 @@ static pbqp_node **node_buckets[4];
 static pbqp_node **reduced_bucket = NULL;
 static int         buckets_filled = 0;
 
+#if KAPS_STATISTIC
+static int dump = 0;
+#endif
+
+/* Forward declarations. */
+static void apply_Brute_Force(pbqp *pbqp);
+
 static void insert_into_edge_bucket(pbqp_edge *edge)
 {
-       unsigned bucket_len = edge_bucket_get_length(edge_bucket);
-
-       if (edge->bucket_index < bucket_len && edge_bucket[edge->bucket_index]
-                       == edge)
+       if (edge_bucket_contains(edge_bucket, edge)) {
                /* Edge is already inserted. */
                return;
+       }
 
-       edge->bucket_index = bucket_len;
-       ARR_APP1(pbqp_edge *, edge_bucket, edge);
+       edge_bucket_insert(&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);
+       edge_bucket_init(&edge_bucket);
+       node_bucket_init(&reduced_bucket);
 
        for (i = 0; i < 4; ++i) {
-               node_buckets[i] = NEW_ARR_F(pbqp_node *, 0);
+               node_bucket_init(&node_buckets[i]);
        }
 }
 
@@ -66,19 +72,19 @@ static void fill_node_buckets(pbqp *pbqp)
        node_len = pbqp->num_nodes;
 
        for (node_index = 0; node_index < node_len; ++node_index) {
-               unsigned   arity;
+               unsigned   degree;
                pbqp_node *node = get_node(pbqp, node_index);
 
                if (!node) continue;
 
-               arity = ARR_LEN(node->edges);
+               degree = pbqp_node_get_degree(node);
 
                /* We have only one bucket for nodes with arity >= 3. */
-               if (arity > 3) {
-                       arity = 3;
+               if (degree > 3) {
+                       degree = 3;
                }
 
-               node_bucket_insert(&node_buckets[arity], node);
+               node_bucket_insert(&node_buckets[degree], node);
        }
 
        buckets_filled = 1;
@@ -131,7 +137,7 @@ static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
 
                        if (min == INF_COSTS) {
                                unsigned edge_index;
-                               unsigned edge_len = ARR_LEN(src_node->edges);
+                               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];
@@ -190,7 +196,7 @@ static void normalize_towards_target(pbqp *pbqp, pbqp_edge *edge)
 
                        if (min == INF_COSTS) {
                                unsigned edge_index;
-                               unsigned edge_len = ARR_LEN(tgt_node->edges);
+                               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];
@@ -205,50 +211,127 @@ static void normalize_towards_target(pbqp *pbqp, pbqp_edge *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;
+       unsigned    degree     = pbqp_node_get_degree(node);
+       /* Assume node lost one incident edge. */
+       unsigned    old_degree = degree + 1;
 
        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   = node_bucket_get_length(old_bucket);
-       old_bucket_index = node->bucket_index;
-
-       if (old_bucket_len <= old_bucket_index || old_bucket[old_bucket_index]
-                       != node) {
-               unsigned bucket_len = node_bucket_get_length(node_buckets[arity]);
+       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(old_bucket_index < bucket_len);
-               assert(node_buckets[arity][old_bucket_index] == node);
+               assert(node_bucket_contains(node_buckets[degree], 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);
+       node_bucket_remove(&node_buckets[old_degree], node);
 
        /* ..and add to new one. */
-       node->bucket_index = node_bucket_get_length(node_buckets[arity]);
-       ARR_APP1(pbqp_node*, node_buckets[arity], node);
+       node_bucket_insert(&node_buckets[degree], node);
+}
+
+#if 0
+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");
+       }
 }
+#endif
 
 static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
 {
@@ -272,11 +355,13 @@ static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
        if (!is_connected(src_node, edge) || !is_connected(tgt_node, edge))
                return;
 
+#if    KAPS_DUMP
        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);
        }
+#endif
 
        src_vec = src_node->costs;
        tgt_vec = tgt_node->costs;
@@ -291,23 +376,35 @@ static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
        mat = edge->costs;
        assert(mat);
 
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                fputs("Input:<br>\n", pbqp->dump_file);
                dump_simplifyedge(pbqp, edge);
        }
+#endif
 
        normalize_towards_source(pbqp, edge);
        normalize_towards_target(pbqp, edge);
 
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                fputs("<br>\nOutput:<br>\n", pbqp->dump_file);
                dump_simplifyedge(pbqp, edge);
        }
+#endif
 
        if (pbqp_matrix_is_zero(mat, src_vec, tgt_vec)) {
+#if    KAPS_DUMP
                if (pbqp->dump_file) {
                        fputs("edge has been eliminated<br>\n", pbqp->dump_file);
                }
+#endif
+
+#if KAPS_STATISTIC
+               if (dump == 0) {
+                       pbqp->num_edges++;
+               }
+#endif
 
                delete_edge(edge);
                reorder_node(src_node);
@@ -315,17 +412,19 @@ static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
        }
 }
 
-void solve_pbqp_heuristical(pbqp *pbqp)
+static void initial_simplify_edges(pbqp *pbqp)
 {
        unsigned node_index;
        unsigned node_len;
 
        assert(pbqp);
 
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                pbqp_dump_input(pbqp);
                dump_section(pbqp->dump_file, 1, "2. Simplification of Cost Matrices");
        }
+#endif
 
        node_len = pbqp->num_nodes;
 
@@ -341,7 +440,7 @@ void solve_pbqp_heuristical(pbqp *pbqp)
                if (!node) continue;
 
                edges = node->edges;
-               edge_len = ARR_LEN(edges);
+               edge_len = pbqp_node_get_degree(node);
 
                for (edge_index = 0; edge_index < edge_len; ++edge_index) {
                        pbqp_edge *edge = edges[edge_index];
@@ -352,57 +451,80 @@ void solve_pbqp_heuristical(pbqp *pbqp)
                        simplify_edge(pbqp, edge);
                }
        }
+}
 
-       /* Put node into bucket representing their arity. */
-       fill_node_buckets(pbqp);
+static num determine_solution(pbqp *pbqp)
+{
+       unsigned node_index;
+       unsigned node_len;
+       num      solution   = 0;
+#if    KAPS_DUMP
+       FILE     *file;
+#endif
 
-       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 {
-                       break;
-               }
-       }
+       assert(pbqp);
 
-       if (pbqp->dump_file) {
-               dump_section(pbqp->dump_file, 1, "4. Determine Solution/Minimum");
-               dump_section(pbqp->dump_file, 2, "4.1. Trivial Solution");
+#if    KAPS_DUMP
+       file = pbqp->dump_file;
+
+       if (file) {
+               dump_section(file, 1, "4. Determine Solution/Minimum");
+               dump_section(file, 2, "4.1. Trivial Solution");
        }
+#endif
 
        /* Solve trivial nodes and calculate solution. */
        node_len = node_bucket_get_length(node_buckets[0]);
+
+#if KAPS_STATISTIC
+       if (dump == 0) {
+               pbqp->num_r0 = node_len;
+       }
+#endif
+
        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,
+               solution       = pbqp_add(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    KAPS_DUMP
+               if (file) {
+                       fprintf(file, "node n%d is set to %d<br>\n", node->index, node->solution);
+                       dump_node(file, node);
                }
+#endif
        }
 
+#if    KAPS_DUMP
+       if (file) {
+               dump_section(file, 2, "Minimum");
+               fprintf(file, "Minimum is equal to %lld.", solution);
+       }
+#endif
+
+       return solution;
+}
+
+static void back_propagate(pbqp *pbqp)
+{
+       unsigned node_index;
+       unsigned node_len   = node_bucket_get_length(reduced_bucket);
+
+       assert(pbqp);
+
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
-               dump_section(pbqp->dump_file, 2, "Minimum");
-               fprintf(pbqp->dump_file, "Minimum is equal to %lld.", pbqp->solution);
                dump_section(pbqp->dump_file, 2, "Back Propagation");
        }
+#endif
 
-       /* Solve reduced nodes. */
-       node_len = node_bucket_get_length(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)) {
+               switch (pbqp_node_get_degree(node)) {
                        case 1:
                                back_propagate_RI(pbqp, node);
                                break;
@@ -414,6 +536,53 @@ void solve_pbqp_heuristical(pbqp *pbqp)
                                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);
+
+#if KAPS_STATISTIC
+       FILE *fh = fopen("solutions.pb", "a");
+       fprintf(fh, "Solution");
+       fclose(fh);
+#endif
+
+       apply_heuristic_reductions(pbqp);
+
+       pbqp->solution = determine_solution(pbqp);
+
+#if KAPS_STATISTIC
+       fh = fopen("solutions.pb", "a");
+       fprintf(fh, ": %lld RE:%u R0:%u R1:%u R2:%u RN/BF:%u\n", pbqp->solution,
+                               pbqp->num_edges, pbqp->num_r0, pbqp->num_r1, pbqp->num_r2,
+                               pbqp->num_rn);
+       fclose(fh);
+#endif
+
+       /* Solve reduced nodes. */
+       back_propagate(pbqp);
 
        free_buckets();
 }
@@ -433,22 +602,26 @@ void apply_RI(pbqp *pbqp)
        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    KAPS_DUMP
        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, node);
-               dump_node(pbqp, other_node);
-               dump_edge(pbqp, edge);
+               dump_node(pbqp->dump_file, node);
+               dump_node(pbqp->dump_file, other_node);
+               dump_edge(pbqp->dump_file, edge);
        }
+#endif
 
        if (is_src) {
                pbqp_matrix_add_to_all_cols(mat, node->costs);
@@ -459,13 +632,21 @@ void apply_RI(pbqp *pbqp)
        }
        disconnect_edge(other_node, edge);
 
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
-               dump_node(pbqp, other_node);
+               dump_node(pbqp->dump_file, other_node);
        }
+#endif
 
        reorder_node(other_node);
 
+#if KAPS_STATISTIC
+       if (dump == 0) {
+               pbqp->num_r1++;
+       }
+#endif
+
        /* Add node to back propagation list. */
        node_bucket_insert(&reduced_bucket, node);
 }
@@ -493,6 +674,7 @@ void apply_RII(pbqp *pbqp)
        unsigned     node_len;
 
        assert(pbqp);
+       assert(pbqp_node_get_degree(node) == 2);
 
        if (src_is_src) {
                src_node = src_edge->tgt;
@@ -523,18 +705,20 @@ void apply_RII(pbqp *pbqp)
                tgt_is_src = tgt_edge->src == node;
        }
 
+#if    KAPS_DUMP
        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);
+               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);
        }
+#endif
 
        src_mat = src_edge->costs;
        tgt_mat = tgt_edge->costs;
@@ -577,6 +761,12 @@ void apply_RII(pbqp *pbqp)
        disconnect_edge(src_node, src_edge);
        disconnect_edge(tgt_node, tgt_edge);
 
+#if KAPS_STATISTIC
+       if (dump == 0) {
+               pbqp->num_r2++;
+       }
+#endif
+
        /* Add node to back propagation list. */
        node_bucket_insert(&reduced_bucket, node);
 
@@ -592,21 +782,67 @@ void apply_RII(pbqp *pbqp)
                reorder_node(tgt_node);
        }
 
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
-               dump_edge(pbqp, edge);
+               dump_edge(pbqp->dump_file, edge);
        }
+#endif
 
        /* Edge has changed so we simplify it. */
        simplify_edge(pbqp, edge);
 }
 
-void apply_RN(pbqp *pbqp)
+static void select_alternative(pbqp_node *node, unsigned selected_index)
+{
+       unsigned  edge_index;
+       unsigned  node_index;
+       unsigned  node_len;
+       vector   *node_vec;
+       unsigned  max_degree = pbqp_node_get_degree(node);
+
+       assert(node);
+       node->solution = selected_index;
+       node_vec = node->costs;
+       node_len = node_vec->len;
+       assert(selected_index < node_len);
+
+       /* Set all other costs to infinity. */
+       for (node_index = 0; node_index < node_len; ++node_index) {
+               if (node_index != selected_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 < max_degree; ++edge_index) {
+               insert_into_edge_bucket(node->edges[edge_index]);
+       }
+}
+
+static pbqp_node *get_node_with_max_degree(void)
 {
        pbqp_node  **bucket       = node_buckets[3];
        unsigned     bucket_len   = node_bucket_get_length(bucket);
        unsigned     bucket_index;
-       pbqp_node   *node         = NULL;
+       unsigned     max_degree   = 0;
+       pbqp_node   *result       = NULL;
+
+       for (bucket_index = 0; bucket_index < bucket_len; ++bucket_index) {
+               pbqp_node *candidate = bucket[bucket_index];
+               unsigned   degree    = pbqp_node_get_degree(candidate);
+
+               if (degree > max_degree) {
+                       result = candidate;
+                       max_degree = degree;
+               }
+       }
+
+       return result;
+}
+
+static unsigned get_local_minimal_alternative(pbqp *pbqp, pbqp_node *node)
+{
        pbqp_edge   *edge;
        vector      *node_vec;
        vector      *vec;
@@ -620,28 +856,10 @@ void apply_RN(pbqp *pbqp)
        int          is_src;
 
        assert(pbqp);
-
-       /* Search for node with maximum degree. */
-       for (bucket_index = 0; bucket_index < bucket_len; ++bucket_index) {
-               pbqp_node *candidate = bucket[bucket_index];
-               unsigned   degree    = ARR_LEN(candidate->edges);
-
-               if (degree > max_degree) {
-                       node = candidate;
-                       max_degree = degree;
-               }
-       }
        assert(node);
        node_vec = node->costs;
        node_len = node_vec->len;
 
-       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 = node_vec->entries[node_index].data;
 
@@ -669,26 +887,223 @@ void apply_RN(pbqp *pbqp)
                }
        }
 
+       return min_index;
+}
+
+void apply_RN(pbqp *pbqp)
+{
+       pbqp_node   *node         = NULL;
+       unsigned     min_index    = 0;
+
+       assert(pbqp);
+
+       /* We want to reduce a node with maximum degree. */
+       node = get_node_with_max_degree();
+       assert(node);
+       assert(pbqp_node_get_degree(node) > 2);
+
+#if    KAPS_DUMP
+       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);
+       }
+#endif
+
+       min_index = get_local_minimal_alternative(pbqp, node);
+
+#if    KAPS_DUMP
        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: %lld<br>\n",
-                                                       min);
        }
-
-       node->solution = min_index;
+#endif
+
+#if KAPS_STATISTIC
+       if (dump == 0) {
+               FILE *fh = fopen("solutions.pb", "a");
+               fprintf(fh, "[%u]", min_index);
+               fclose(fh);
+               pbqp->num_rn++;
+       }
+#endif
 
        /* Now that we found the local minimum set all other costs to infinity. */
+       select_alternative(node, min_index);
+}
+
+static void apply_brute_force_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_Brute_Force(pbqp);
+               } else {
+                       return;
+               }
+       }
+}
+
+static unsigned get_minimal_alternative(pbqp *pbqp, pbqp_node *node)
+{
+       vector      *node_vec;
+       unsigned     node_index;
+       unsigned     node_len;
+       unsigned     min_index    = 0;
+       num          min          = INF_COSTS;
+       unsigned     bucket_index;
+
+       assert(pbqp);
+       assert(node);
+       node_vec     = node->costs;
+       node_len     = node_vec->len;
+       bucket_index = node->bucket_index;
+
        for (node_index = 0; node_index < node_len; ++node_index) {
-               if (node_index != min_index) {
-                       node_vec->entries[node_index].data = INF_COSTS;
+               pbqp_node_bucket bucket_deg3;
+               num              value;
+               unsigned         bucket_0_length;
+               unsigned         bucket_red_length;
+
+               char *tmp = obstack_finish(&pbqp->obstack);
+
+               node_bucket_init(&bucket_deg3);
+
+               /* Some node buckets and the edge bucket should be empty. */
+               assert(node_bucket_get_length(node_buckets[1]) == 0);
+               assert(node_bucket_get_length(node_buckets[2]) == 0);
+               assert(edge_bucket_get_length(edge_bucket)     == 0);
+
+               /* char *tmp = obstack_finish(&pbqp->obstack); */
+
+               /* Save current PBQP state. */
+               node_bucket_copy(&bucket_deg3, node_buckets[3]);
+               node_bucket_shrink(&node_buckets[3], 0);
+               node_bucket_deep_copy(pbqp, &node_buckets[3], bucket_deg3);
+               node_bucket_update(pbqp, node_buckets[3]);
+               bucket_0_length   = node_bucket_get_length(node_buckets[0]);
+               bucket_red_length = node_bucket_get_length(reduced_bucket);
+
+               /* Select alternative and solve PBQP recursively. */
+               select_alternative(node_buckets[3][bucket_index], node_index);
+               apply_brute_force_reductions(pbqp);
+
+               value = determine_solution(pbqp);
+
+               if (value < min) {
+                       min = value;
+                       min_index = node_index;
                }
+
+               /* Some node buckets and the edge bucket should still be empty. */
+               assert(node_bucket_get_length(node_buckets[1]) == 0);
+               assert(node_bucket_get_length(node_buckets[2]) == 0);
+               assert(edge_bucket_get_length(edge_bucket)     == 0);
+
+               /* Clear modified buckets... */
+               node_bucket_shrink(&node_buckets[3], 0);
+
+               /* ... and restore old PBQP state. */
+               node_bucket_shrink(&node_buckets[0], bucket_0_length);
+               node_bucket_shrink(&reduced_bucket, bucket_red_length);
+               node_bucket_copy(&node_buckets[3], bucket_deg3);
+               node_bucket_update(pbqp, node_buckets[3]);
+
+               /* Free copies. */
+               /* obstack_free(&pbqp->obstack, tmp); */
+               node_bucket_free(&bucket_deg3);
+
+               obstack_free(&pbqp->obstack, tmp);
        }
 
-       /* Add all incident edges to edge bucket, since they are now independent. */
-       for (edge_index = 0; edge_index < max_degree; ++edge_index) {
-               insert_into_edge_bucket(node->edges[edge_index]);
+       return min_index;
+}
+
+void apply_Brute_Force(pbqp *pbqp)
+{
+       pbqp_node   *node         = NULL;
+       unsigned     min_index    = 0;
+
+       assert(pbqp);
+
+       /* We want to reduce a node with maximum degree. */
+       node = get_node_with_max_degree();
+       assert(node);
+       assert(pbqp_node_get_degree(node) > 2);
+
+#if    KAPS_DUMP
+       if (pbqp->dump_file) {
+               char     txt[100];
+               sprintf(txt, "BF-Reduction of Node n%d", node->index);
+               dump_section(pbqp->dump_file, 2, txt);
+               pbqp_dump_graph(pbqp);
        }
+#endif
+
+#if KAPS_STATISTIC
+       dump++;
+#endif
+
+       min_index = get_minimal_alternative(pbqp, node);
+       node = pbqp->nodes[node->index];
+
+#if    KAPS_DUMP
+       if (pbqp->dump_file) {
+               fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
+                                       node->index, min_index);
+       }
+#endif
+
+#if KAPS_STATISTIC
+       dump--;
+       if (dump == 0) {
+               FILE *fh = fopen("solutions.pb", "a");
+               fprintf(fh, "[%u]", min_index);
+               fclose(fh);
+               pbqp->num_bf++;
+       }
+#endif
+
+       /* Now that we found the minimum set all other costs to infinity. */
+       select_alternative(node, min_index);
+}
+
+void solve_pbqp_brute_force(pbqp *pbqp)
+{
+       /* Reduce nodes degree ... */
+       initial_simplify_edges(pbqp);
+
+       /* ... and put node into bucket representing their degree. */
+       fill_node_buckets(pbqp);
+
+#if KAPS_STATISTIC
+       FILE *fh = fopen("solutions.pb", "a");
+       fprintf(fh, "Solution");
+       fclose(fh);
+#endif
+
+       apply_brute_force_reductions(pbqp);
+
+       pbqp->solution = determine_solution(pbqp);
+
+#if KAPS_STATISTIC
+       fh = fopen("solutions.pb", "a");
+       fprintf(fh, ": %lld RE:%u R0:%u R1:%u R2:%u RN/BF:%u\n", pbqp->solution,
+                       pbqp->num_edges, pbqp->num_r0, pbqp->num_r1, pbqp->num_r2,
+                       pbqp->num_bf);
+       fclose(fh);
+#endif
+
+       /* Solve reduced nodes. */
+       back_propagate(pbqp);
+
+       free_buckets();
 }
 
 void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
@@ -710,17 +1125,26 @@ void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
        if (is_src) {
                other = edge->tgt;
                assert(other);
-               vector_add_matrix_col(vec, mat, other->solution);
+
+               /* Update pointer for brute force solver. */
+               other = pbqp->nodes[other->index];
+
+               node->solution = pbqp_matrix_get_col_min_index(mat, other->solution, vec);
        } else {
                other = edge->src;
                assert(other);
-               vector_add_matrix_row(vec, mat, other->solution);
+
+               /* Update pointer for brute force solver. */
+               other = pbqp->nodes[other->index];
+
+               node->solution = pbqp_matrix_get_row_min_index(mat, other->solution, vec);
        }
 
-       node->solution = vector_get_min_index(vec);
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
        }
+#endif
 }
 
 void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
@@ -769,6 +1193,10 @@ void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
                tgt_is_src = tgt_edge->src == node;
        }
 
+       /* Update pointer for brute force solver. */
+       src_node = pbqp->nodes[src_node->index];
+       tgt_node = pbqp->nodes[tgt_node->index];
+
        src_mat = src_edge->costs;
        tgt_mat = tgt_edge->costs;
 
@@ -792,9 +1220,12 @@ void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
        }
 
        node->solution = vector_get_min_index(vec);
+
+#if    KAPS_DUMP
        if (pbqp->dump_file) {
                fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
        }
+#endif
 
        obstack_free(&pbqp->obstack, vec);
 }
@@ -803,11 +1234,7 @@ 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 = node_bucket_get_length(reduced_bucket);
-       unsigned bucket_index  = node->bucket_index;
+       if (pbqp_node_get_degree(node) == 0) return 1;
 
-       return bucket_index < bucket_length && reduced_bucket[bucket_index] == node;
+       return node_bucket_contains(reduced_bucket, node);
 }