mempool: use FeeFrac for calculating ancestor score

Author: theStack

src/txmempool.h

@@ -154,37 +154,25 @@ class CompareTxMemPoolEntryByAncestorFee
     template<typename T>
     bool operator()(const T& a, const T& b) const
     {
-        double a_mod_fee, a_size, b_mod_fee, b_size;
-
-        GetModFeeAndSize(a, a_mod_fee, a_size);
-        GetModFeeAndSize(b, b_mod_fee, b_size);
-
-        // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
-        double f1 = a_mod_fee * b_size;
-        double f2 = a_size * b_mod_fee;
+        FeeFrac f1 = GetModFeeAndSize(a);
+        FeeFrac f2 = GetModFeeAndSize(b);
 
-        if (f1 == f2) {
+        if (FeeRateCompare(f1, f2) == 0) {
             return a.GetTx().GetHash() < b.GetTx().GetHash();
         }
         return f1 > f2;
     }
 
     // Return the fee/size we're using for sorting this entry.
     template <typename T>
-    void GetModFeeAndSize(const T &a, double &mod_fee, double &size) const
+    FeeFrac GetModFeeAndSize(const T &a) const
     {
         // Compare feerate with ancestors to feerate of the transaction, and
         // return the fee/size for the min.
-        double f1 = (double)a.GetModifiedFee() * a.GetSizeWithAncestors();
-        double f2 = (double)a.GetModFeesWithAncestors() * a.GetTxSize();
-
-        if (f1 > f2) {
-            mod_fee = a.GetModFeesWithAncestors();
-            size = a.GetSizeWithAncestors();
-        } else {
-            mod_fee = a.GetModifiedFee();
-            size = a.GetTxSize();
-        }
+        return std::min<FeeFrac>(
+            FeeFrac(a.GetModFeesWithAncestors(), a.GetSizeWithAncestors()),
+            FeeFrac(a.GetModifiedFee(), a.GetTxSize())
+        );
     }
 };