add FinalState Getter

Author: qindazhu

k2/csrc/fsa.h

@@ -112,6 +112,12 @@ struct Fsa {
     return !arc_indexes.empty() ? (static_cast<int32_t>(arc_indexes.size()) - 1)
                                 : 0;
   }
+
+  int32_t FinalState() const {
+    // It's not valid to call this if the FSA is empty.
+    CHECK(!arc_indexes.empty());
+    return arc_indexes.size() - 2;
+  }
 };
 
 /*

k2/csrc/util.h

@@ -34,7 +34,7 @@ struct PairHash {
 };
 
 static const double kMinLogDiffDouble = log(DBL_EPSILON);  // negative!
-static const float kMinLogDiffFloat = log(FLT_EPSILON);    // negative!
+static const float kMinLogDiffFloat = logf(FLT_EPSILON);   // negative!
 
 // returns log(exp(x) + exp(y)).
 inline double LogAdd(double x, double y) {
@@ -71,7 +71,7 @@ inline float LogAdd(float x, float y) {
 
   if (diff >= kMinLogDiffFloat) {
     float res;
-    res = x + log1p(exp(diff));
+    res = x + log1pf(expf(diff));
     return res;
   } else {
     return x;  // return the larger one.