2 files changed, 9 insertions, 5 deletions
diff --git a/decoder/ff_fsa.h b/decoder/ff_fsa.h
index 0a7aebde..e199ec04 100755
--- a/decoder/ff_fsa.h
+++ b/decoder/ff_fsa.h
@@ -136,7 +136,7 @@ public:
 
   // NOTE: if you want to e.g. track statistics, cache, whatever, cast const away or use mutable members
   inline void Scan(SentenceMetadata const& smeta,const Hypergraph::Edge& edge,WordID w,void const* state,void *next_state,FeatureVector *features) const {
-    features->add_value(fid_,Scan1(w,state,next_state));
+    features->maybe_add(fid_,Scan1(w,state,next_state));
   }
 
   // don't set state-bytes etc. in ctor because it may depend on parsing param string
@@ -244,7 +244,7 @@ public:
   int markov_order() const { return 1; }
   Featval ScanT1(WordID w,int prevlen,int &len) const { return 0; }
   inline void ScanT(SentenceMetadata const& smeta,const Hypergraph::Edge& edge,WordID w,int prevlen,int &len,FeatureVector *features) const {
-    features->add_value(d().fid_,d().ScanT1(w,prevlen,len));
+    features->maybe_add(d().fid_,d().ScanT1(w,prevlen,len));
   }
 
   inline void Scan(SentenceMetadata const& smeta,const Hypergraph::Edge& edge,WordID w,void const* st,void *next_state,FeatureVector *features) const {
diff --git a/decoder/sparse_vector.h b/decoder/sparse_vector.h
index ec623c6e..0325c1ee 100644
--- a/decoder/sparse_vector.h
+++ b/decoder/sparse_vector.h
@@ -115,15 +115,19 @@ public:
     values_[index] = value;
   }
 
-    void add_value(int index, const T &value) {
-      if (!value) return;
+  inline void maybe_add(int index, const T& value) {
+    if (value) add_value(index,value);
+  }
+
+    T& add_value(int index, const T &value) {
 #if 1
-      values_[index]+=value;
+      return values_[index]+=value;
 #else
       // this is not really going to be any faster, and we already rely on default init = 0 init
       std::pair<typename MapType::iterator,bool> art=values_.insert(std::make_pair(index,value));
       T &val=art.first->second;
       if (!art.second) val += value; // already existed
+      return val;
 #endif
     }