From ac9c113bd2a2bb5001391a486d010189368f51f3 Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Tue, 24 Jun 2025 02:20:03 +0200
Subject: [PATCH 1/3] mempool: use `FeeFrac` for calculating descendant score

---
 src/txmempool.h | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/src/txmempool.h b/src/txmempool.h
index 10acb2aa22f..cca38002720 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -93,36 +93,24 @@ class CompareTxMemPoolEntryByDescendantScore
 public:
     bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
     {
-        double a_mod_fee, a_size, b_mod_fee, b_size;
+        FeeFrac f1 = GetModFeeAndSize(a);
+        FeeFrac f2 = GetModFeeAndSize(b);
 
-        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;
-
-        if (f1 == f2) {
+        if (FeeRateCompare(f1, f2) == 0) {
             return a.GetTime() >= b.GetTime();
         }
         return f1 < f2;
     }
 
     // Return the fee/size we're using for sorting this entry.
-    void GetModFeeAndSize(const CTxMemPoolEntry &a, double &mod_fee, double &size) const
+    FeeFrac GetModFeeAndSize(const CTxMemPoolEntry &a) const
     {
         // Compare feerate with descendants to feerate of the transaction, and
         // return the fee/size for the max.
-        double f1 = (double)a.GetModifiedFee() * a.GetSizeWithDescendants();
-        double f2 = (double)a.GetModFeesWithDescendants() * a.GetTxSize();
-
-        if (f2 > f1) {
-            mod_fee = a.GetModFeesWithDescendants();
-            size = a.GetSizeWithDescendants();
-        } else {
-            mod_fee = a.GetModifiedFee();
-            size = a.GetTxSize();
-        }
+        return std::max<FeeFrac>(
+            FeeFrac(a.GetModFeesWithDescendants(), a.GetSizeWithDescendants()),
+            FeeFrac(a.GetModifiedFee(), a.GetTxSize())
+        );
     }
 };
 

From 3322b3a05954a1bac9f49a92e3bb35d2cbd20029 Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Tue, 24 Jun 2025 02:34:29 +0200
Subject: [PATCH 2/3] mempool: use `FeeFrac` for calculating ancestor score

---
 src/txmempool.h | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/src/txmempool.h b/src/txmempool.h
index cca38002720..466792a1e6d 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -154,16 +154,10 @@ public:
     template<typename T>
     bool operator()(const T& a, const T& b) const
     {
-        double a_mod_fee, a_size, b_mod_fee, b_size;
+        FeeFrac f1 = GetModFeeAndSize(a);
+        FeeFrac f2 = GetModFeeAndSize(b);
 
-        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;
-
-        if (f1 == f2) {
+        if (FeeRateCompare(f1, f2) == 0) {
             return a.GetTx().GetHash() < b.GetTx().GetHash();
         }
         return f1 > f2;
@@ -171,20 +165,14 @@ public:
 
     // 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())
+        );
     }
 };
 

From 922adf66ac7420e21ea171d3586ea84554e5d91b Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Tue, 24 Jun 2025 02:49:31 +0200
Subject: [PATCH 3/3] mempool: use `FeeFrac` for calculating regular score

---
 src/txmempool.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/txmempool.h b/src/txmempool.h
index 466792a1e6d..83926927cd6 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -126,9 +126,9 @@ class CompareTxMemPoolEntryByScore
 public:
     bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
     {
-        double f1 = (double)a.GetFee() * b.GetTxSize();
-        double f2 = (double)b.GetFee() * a.GetTxSize();
-        if (f1 == f2) {
+        FeeFrac f1(a.GetFee(), a.GetTxSize());
+        FeeFrac f2(b.GetFee(), b.GetTxSize());
+        if (FeeRateCompare(f1, f2) == 0) {
             return b.GetTx().GetHash() < a.GetTx().GetHash();
         }
         return f1 > f2;