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Merge bitcoin/bitcoin#32799: mempool: use FeeFrac for ancestor/descendant score comparators

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922adf66ac7420e21ea171d3586ea84554e5d91b mempool: use `FeeFrac` for calculating regular score (Sebastian Falbesoner)
3322b3a05954a1bac9f49a92e3bb35d2cbd20029 mempool: use `FeeFrac` for calculating ancestor score (Sebastian Falbesoner)
ac9c113bd2a2bb5001391a486d010189368f51f3 mempool: use `FeeFrac` for calculating descendant score (Sebastian Falbesoner)

Pull request description:

  Rather than determining fee-rates for the mempool index scores and comparators manually in a rather tedious way (even involving floating-points), use the `FeeFrac` class [1] to simplify and deduplicate the code. Note that though this is intended to be a refactoring PR, there might be subtle differences in behaviour due to floating-point arithmetic involved in the original code (to avoid overflows at the cost of precision loss), but these shouldn't matter.

  [1] introduced in PR #29242, commit ce8e22542ed0b4fa5794d3203207146418d59473

ACKs for top commit:
  ismaelsadeeq:
    Code review ACK 922adf66ac7420e21ea171d3586ea84554e5d91b
  glozow:
    ACK 922adf66ac7420e21ea171d3586ea84554e5d91b

Tree-SHA512: 6c3a9436f2be668aa8561b40c1b93efa7dc97b4ef354e98233ac3d3286a88804668164a55f2fcce4239fee5830e4e70f520e6285b667b87baa65c7cec09159cf
This commit is contained in:
merge-script 2025-07-09 15:15:53 -04:00
commit 2cad7226c2
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GPG Key ID: BA03F4DBE0C63FB4
1 changed files with 19 additions and 43 deletions
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62
src/txmempool.h
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@ -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())
);
}
};
@ -138,9 +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;
@ -166,16 +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;
@ -183,20 +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())
);
}
};