3 files changed, 142 insertions, 0 deletions
diff --git a/lib/nlp_ruby.rb b/lib/nlp_ruby.rb
index a3f9f1a..f57a302 100755
--- a/lib/nlp_ruby.rb
+++ b/lib/nlp_ruby.rb
@@ -9,6 +9,7 @@ require 'nlp_ruby/dag'
 require 'nlp_ruby/semirings'
 require 'nlp_ruby/bleu'
 require 'nlp_ruby/misc'
+require 'nlp_ruby/hg'
 
 STDIN.set_encoding 'utf-8'
 STDOUT.set_encoding 'utf-8'
diff --git a/lib/nlp_ruby/hg.rb b/lib/nlp_ruby/hg.rb
new file mode 100644
index 0000000..b49cc6e
--- /dev/null
+++ b/lib/nlp_ruby/hg.rb
@@ -0,0 +1,131 @@
+#!/usr/bin/env ruby
+
+require 'nlp_ruby'
+require 'json'
+
+module HG
+
+
+class HG::Node
+  attr_accessor :label, :cat, :outgoing, :incoming, :score
+
+  def initialize label=nil, cat=nil, outgoing=[], incoming=[], score=nil
+    @label    = label
+    @cat      = cat
+    @outgoing = outgoing
+    @incoming = incoming
+    @score    = nil
+  end
+
+  def to_s
+    "Node<label:\"#{@label}\", cat:\"#{@cat}\", outgoing:#{@outgoing.size}, incoming:#{@incoming.size}>"
+  end
+end
+
+class HG::Hypergraph
+  attr_accessor :nodes, :edges
+
+  def initialize nodes=[], edges=[]
+    @nodes = nodes
+    @edges = edges
+  end
+
+  def arity
+    @edges.map { |e| e.arity }.max
+  end
+
+  def to_s
+    "Hypergraph<nodes:[#{@nodes.to_s}], edges:[#{@edges.to_s}], arity:#{arity}>"
+  end
+end
+
+class HG::Hyperedge
+  attr_accessor :head, :tails, :weight, :f, :mark
+
+  def initialize head=nil, tails=[], weight=0.0, f={}
+    @head   = head
+    @tails  = tails
+    @weight = weight
+    @f      = f
+    @mark   = 0
+  end
+
+  def arity
+    return @tails.size
+  end
+
+  def marked?
+    arity == @mark
+  end
+
+  def to_s
+    "Hyperedge<head:\"#{@head.label}\", tails:#{@tails.map{|n|n.label}}, arity:#{arity}, weight:#{@weight}, f:#{f.to_s}, mark:#{@mark}>"
+  end
+end
+
+def HG::topological_sort nodes
+  sorted = []
+  s = nodes.reject { |n| !n.incoming.empty? }
+  while !s.empty?
+    sorted << s.shift
+    sorted.last.outgoing.each { |e|
+      next if e.marked?
+      e.mark += 1
+      s << e.head if e.head.incoming.reject{ |f| f.mark==f.arity }.empty?
+    }
+  end
+  return sorted
+end
+
+def HG::init nodes, semiring, root
+  nodes.each { |n| n.score=semiring.null }
+  root.score = semiring.one
+end
+
+def HG::viterbi hypergraph, root, semiring=ViterbiSemiring.new
+  toposorted = topological_sort hypergraph.nodes
+  init toposorted, semiring, root
+  toposorted.each { |n|
+    n.incoming.each { |e|
+      s = semiring.one
+      e.tails.each { |m|
+        s = semiring.multiply.call(s, m.score)
+      }
+      n.score = semiring.add.call(n.score, semiring.multiply.call(s, e.weight))
+    }
+  }
+end
+
+def HG::read_hypergraph_from_json fn, semiring=RealSemiring.new, log_weights=false
+  nodes = []
+  edges = []
+  nodes_by_label = {}
+  nodes_by_index = []
+  h = JSON.parse File.new(fn).read
+  w = SparseVector.from_h h['weights']
+  h['nodes'].each { |i|
+    n = Node.new i['label'], i['cat']
+    nodes << n
+    nodes_by_label[n.label] = n
+    nodes_by_index << n
+  }
+  h['edges'].each { |i|
+    e = Hyperedge.new nodes_by_label[i['head']], i['tails'].map{|j| nodes_by_label[j]}.to_a, semiring.convert.call(i['weight'].to_f)
+    e.f = SparseVector.from_h i['f']
+    if log_weights
+      e.weight = Math.exp(w.dot(e.f))
+    else
+      e.weight = w.dot(e.f)
+    end
+    e.tails.each { |m|
+      m.outgoing << e
+    }
+    e.head.incoming << e
+    edges << e
+  }
+  return Hypergraph.new(nodes, edges), nodes_by_label, nodes_by_index
+end
+
+
+end #module
+
diff --git a/lib/nlp_ruby/semirings.rb b/lib/nlp_ruby/semirings.rb
index 83551a9..fda4683 100644
--- a/lib/nlp_ruby/semirings.rb
+++ b/lib/nlp_ruby/semirings.rb
@@ -26,6 +26,16 @@ class ViterbiSemiring < Semiring
   end
 end
 
+class ViterbiLogSemiring < Semiring
+  def initialize
+    @add = Proc.new { |a,b| [a,b].max }
+    @multiply =  Proc.new { |a,b| a+b }
+    @one = 0.0
+    @null = -1.0/0.0
+    @convert = Proc.new { |v| v }
+  end
+end
+
 class InsideSemiring < Semiring
   def initialize
     @add = Proc.new { |a,b| a+b }