Add normalize flag in default message update (#195)

Author: JoeyT1994

src/caches/beliefpropagationcache.jl

@@ -16,11 +16,11 @@ using NDTensors: NDTensors
 
 default_message(elt, inds_e) = ITensor[denseblocks(delta(elt, i)) for i in inds_e]
 default_messages(ptn::PartitionedGraph) = Dictionary()
-function default_message_update(contract_list::Vector{ITensor}; kwargs...)
+function default_message_update(contract_list::Vector{ITensor}; normalize=true, kwargs...)
   sequence = optimal_contraction_sequence(contract_list)
   updated_messages = contract(contract_list; sequence, kwargs...)
   message_norm = norm(updated_messages)
-  if !iszero(message_norm)
+  if normalize && !iszero(message_norm)
     updated_messages /= message_norm
   end
   return ITensor[updated_messages]