Merge branch 'fix_mempool_hist' into HEAD

src/Mempool.cpp

@@ -23,6 +23,7 @@
 #include <cassert>
 #include <functional>
 #include <map>
+#include <optional>
 #include <utility>
 
 void Mempool::clear() {
@@ -33,32 +34,42 @@ void Mempool::clear() {
     hashXTxs.rehash(0);
 }
 
-auto Mempool::calcCompactFeeHistogram(double binSize) const -> FeeHistogramVec
+auto Mempool::calcCompactFeeHistogram(unsigned binSizeBytes) const -> FeeHistogramVec
 {
-    // this algorithm is taken from:
-    // https://github.com/Electron-Cash/electrumx/blob/fbd00416d804c286eb7de856e9399efb07a2ceaf/electrumx/server/mempool.py#L139
+    // This algorithm is taken from:
+    // https://github.com/spesmilo/electrumx/blob/bbd985a95db63cada13254bb766f174e9ab674d0/electrumx/server/mempool.py#L154
     FeeHistogramVec ret;
     std::map<unsigned, unsigned, std::greater<unsigned>> histogram; // sorted map, descending order by key
 
     for (const auto & [txid, tx] : txs) {
+        if (tx->fee < bitcoin::Amount::zero()) continue; // skip negative fees (coinbase txn, etc)
         const auto feeRate = unsigned(tx->fee / bitcoin::Amount::satoshi()) // sats
                              /  std::max(tx->sizeBytes, 1u); // per byte
         histogram[feeRate] += tx->sizeBytes; // accumulate size by feeRate
     }
 
-    // now, compact the bins
+    // Now, compact the bins
     ret.reserve(8);
     unsigned cumSize = 0;
-    double r = 0.;
+    double binSize = static_cast<double>(binSizeBytes);
+    std::optional<unsigned> prevFeeRate;
 
     for (const auto & [feeRate, size] : histogram) {
+        // If there is a big lump of txns at this specific size,
+        // add the previous item now (if not added already)
+        if (double(size) > 2.0 * binSize && prevFeeRate && cumSize > 0) {
+            ret.emplace_back(*prevFeeRate, cumSize);
+            cumSize = 0;
+            binSize *= 1.1;
+        }
+        // Now work on perhaps adding this item
         cumSize += size;
-        if (cumSize + r > binSize) {
-            ret.push_back(FeeHistogramItem{feeRate, cumSize});
-            r += double(cumSize) - binSize;
+        if (cumSize > binSize) {
+            ret.emplace_back(feeRate, cumSize);
             cumSize = 0;
             binSize *= 1.1;
         }
+        prevFeeRate = feeRate;
     }
     ret.shrink_to_fit(); // save memory
     return ret;

src/Mempool.h

@@ -209,12 +209,13 @@ struct Mempool
     struct FeeHistogramItem {
         unsigned feeRate = 0; // in sats/B, quotient truncated to uint.
         unsigned cumulativeSize = 0; // bin size, cumulative bytes
+        FeeHistogramItem(unsigned fr, unsigned cs) : feeRate{fr}, cumulativeSize{cs} {}
     };
     using FeeHistogramVec = std::vector<FeeHistogramItem>;
     /// This function is potentially going to take a couple of ms at worst on very large mempools.  Even a 1.5k tx
     /// mempool takes under 1 ms on average hardware, so it's very fast. Storage calls this in refreshMempoolHistogram
     /// from a periodic background task kicked off in Controller.
-    FeeHistogramVec calcCompactFeeHistogram(double binSize = 1e5 /* binSize in bytes */) const;
+    FeeHistogramVec calcCompactFeeHistogram(unsigned binSize = 30'000 /* binSize in bytes */) const;
 
     // -- Dump (for JSONesque debug support)
 

src/Servers.h

@@ -334,7 +334,7 @@ protected slots:
     [[nodiscard]] static QVariantMap unspentItemToVariantMap(const Storage::UnspentItem &);
 };
 
-/// Implements the ElectrumX/ElectronX JSON-RPC protocol, version 1.4.4.
+/// Implements the Electrum Cash JSON-RPC protocol: https://electrum-cash-protocol.readthedocs.io/en/latest/index.html
 /// See also ServerSSL (subclass) which is identical but serves to SSL clients.  (This class serves to TCP clients).
 class Server : public ServerBase
 {