BP Efficiency Improvement (#194)

Author: JoeyT1994

src/caches/beliefpropagationcache.jl

@@ -106,7 +106,7 @@ end
 
 function message(bp_cache::BeliefPropagationCache, edge::PartitionEdge)
   mts = messages(bp_cache)
-  return get(mts, edge, default_message(bp_cache, edge))
+  return get(() -> default_message(bp_cache, edge), mts, edge)
 end
 function messages(bp_cache::BeliefPropagationCache, edges; kwargs...)
   return map(edge -> message(bp_cache, edge; kwargs...), edges)
@@ -152,15 +152,16 @@ end
 function environment(bp_cache::BeliefPropagationCache, verts::Vector)
   partition_verts = partitionvertices(bp_cache, verts)
   messages = environment(bp_cache, partition_verts)
-  central_tensors = ITensor[
-    tensornetwork(bp_cache)[v] for v in setdiff(vertices(bp_cache, partition_verts), verts)
-  ]
+  central_tensors = factors(bp_cache, setdiff(vertices(bp_cache, partition_verts), verts))
   return vcat(messages, central_tensors)
 end
 
+function factors(bp_cache::BeliefPropagationCache, verts::Vector)
+  return ITensor[tensornetwork(bp_cache)[v] for v in verts]
+end
+
 function factor(bp_cache::BeliefPropagationCache, vertex::PartitionVertex)
-  ptn = partitioned_tensornetwork(bp_cache)
-  return collect(eachtensor(subgraph(ptn, vertex)))
+  return factors(bp_cache, vertices(bp_cache, vertex))
 end
 
 """