target context feature base class

moses/FF/VW/VWFeatureBase.h

@@ -8,6 +8,7 @@
 #include "moses/TranslationTask.h"
 #include "moses/Util.h"
 #include "moses/FF/StatelessFeatureFunction.h"
+#include "moses/FF/FFState.h"
 
 namespace Moses
 {
@@ -104,6 +105,13 @@ public:
                           , const TargetPhrase &targetPhrase
                           , Discriminative::Classifier &classifier) const = 0;
 
+  // Overload to process target-context dependent features, these features are
+  // evaluated during decoding. For efficiency, features are not fed directly into
+  // the classifier object but instead output in the vector "features" and managed
+  // separately in VW.h.
+  virtual FFState *operator()(const Hypothesis &hypo
+                              , std::vector<StringPiece> &features) const = 0;
+
 protected:
   std::vector<FactorType> m_sourceFactors, m_targetFactors;
 

moses/FF/VW/VWFeatureContext.h

@@ -0,0 +1,49 @@
+#pragma once
+
+#include <string>
+#include "VWFeatureBase.h"
+#include "moses/InputType.h"
+
+namespace Moses
+{
+
+// Inherit from this for source-dependent classifier features. They will
+// automatically register with the classifier class named VW0 or one or more
+// names specified by the used-by=name1,name2,... parameter.
+//
+// The classifier gets a full list by calling
+// VWFeatureBase::GetTargetContextFeatures(GetScoreProducerDescription())
+
+
+class VWFeatureContext : public VWFeatureBase
+{
+public:
+  VWFeatureContext(const std::string &line)
+    : VWFeatureBase(line, vwft_targetContext) {
+  }
+
+  // Gets its pure virtual functions from VWFeatureBase
+
+  virtual void operator()(const InputType &input
+                          , const InputPath &inputPath
+                          , const TargetPhrase &targetPhrase
+                          , Discriminative::Classifier &classifier) const {
+  }
+
+  virtual void operator()(const InputType &input
+                          , const InputPath &inputPath
+                          , const Range &sourceRange
+                          , Discriminative::Classifier &classifier) const {
+  }
+
+  virtual void SetParameter(const std::string& key, const std::string& value) {
+    VWFeatureBase::SetParameter(key, value);
+  }
+
+protected:
+  inline std::string GetWord(const InputType &input, size_t pos) const {
+    return input.GetWord(pos).GetString(m_sourceFactors, false);
+  }
+};
+
+}

moses/FF/VW/VWFeatureSource.h

@@ -30,6 +30,11 @@ public:
                           , Discriminative::Classifier &classifier) const {
   }
 
+  virtual FFState *operator()(const Hypothesis &hypo
+                              , std::vector<StringPiece> &features) const {
+    return NULL;
+  }
+
   virtual void SetParameter(const std::string& key, const std::string& value) {
     VWFeatureBase::SetParameter(key, value);
   }

moses/FF/VW/VWFeatureTarget.h

@@ -28,6 +28,11 @@ public:
                           , Discriminative::Classifier &classifier) const {
   }
 
+  virtual FFState *operator()(const Hypothesis &hypo
+                              , std::vector<StringPiece> &features) const {
+    return NULL;
+  }
+
   virtual void SetParameter(const std::string& key, const std::string& value) {
     VWFeatureBase::SetParameter(key, value);
   }