Apply RN reduction on a node with maximum degree.

[r22916]

diff --git a/heuristical.c b/heuristical.c
index d7f6a39..cbc61e0 100644 (file)
--- a/heuristical.c
+++ b/heuristical.c
@@ -622,23 +622,38 @@ void apply_RII(pbqp *pbqp)
 
 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_node  **bucket       = node_buckets[3];
+       unsigned     bucket_len   = ARR_LEN(bucket);
+       unsigned     bucket_index;
+       pbqp_node   *node         = NULL;
        pbqp_edge   *edge;
-       vector      *node_vec   = node->costs;
+       vector      *node_vec;
        vector      *vec;
        pbqp_matrix *mat;
        unsigned     edge_index;
-       unsigned     edge_len   = ARR_LEN(node->edges);
+       unsigned     max_degree   = 0;
        unsigned     node_index;
-       unsigned     node_len   = node_vec->len;
-       unsigned     min_index  = 0;
-       num          min        = INF_COSTS;
+       unsigned     node_len;
+       unsigned     min_index    = 0;
+       num          min          = INF_COSTS;
        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);
@@ -649,7 +664,7 @@ void apply_RN(pbqp *pbqp)
        for (node_index = 0; node_index < node_len; ++node_index) {
                num value = node_vec->entries[node_index].data;
 
-               for (edge_index = 0; edge_index < edge_len; ++edge_index) {
+               for (edge_index = 0; edge_index < max_degree; ++edge_index) {
                        edge   = node->edges[edge_index];
                        mat    = edge->costs;
                        is_src = edge->src == node;
@@ -690,7 +705,7 @@ void apply_RN(pbqp *pbqp)
        }
 
        /* Add all incident edges to edge bucket, since they are now independent. */
-       for (edge_index = 0; edge_index < edge_len; ++edge_index) {
+       for (edge_index = 0; edge_index < max_degree; ++edge_index) {
                insert_into_edge_bucket(node->edges[edge_index]);
        }
 }