txgraph: make number of acceptable iterations configurable (feature)

src/test/fuzz/txgraph.cpp

@@ -272,9 +272,11 @@ FUZZ_TARGET(txgraph)
     auto max_count = provider.ConsumeIntegralInRange<DepGraphIndex>(1, MAX_CLUSTER_COUNT_LIMIT);
     // And the maximum combined size of transactions per cluster.
     auto max_size = provider.ConsumeIntegralInRange<uint64_t>(1, 0x3fffff * MAX_CLUSTER_COUNT_LIMIT);
+    // And the number of iterations to consider a cluster acceptably linearized.
+    auto acceptable_iters = provider.ConsumeIntegralInRange<uint64_t>(0, 10000);
 
     // Construct a real graph, and a vector of simulated graphs (main, and possibly staging).
-    auto real = MakeTxGraph(max_count, max_size);
+    auto real = MakeTxGraph(max_count, max_size, acceptable_iters);
     std::vector<SimTxGraph> sims;
     sims.reserve(2);
     sims.emplace_back(max_count, max_size);

src/txgraph.cpp

@@ -247,6 +247,8 @@ private:
     const DepGraphIndex m_max_cluster_count;
     /** This TxGraphImpl's maximum cluster size limit. */
     const uint64_t m_max_cluster_size;
+    /** The number of linearization improvements steps needed for it to be considered acceptable. */
+    const uint64_t m_acceptable_iters;
 
     /** Information about one group of Clusters to be merged. */
     struct GroupEntry
@@ -443,9 +445,10 @@ private:
 
 public:
     /** Construct a new TxGraphImpl with the specified limits. */
-    explicit TxGraphImpl(DepGraphIndex max_cluster_count, uint64_t max_cluster_size) noexcept :
+    explicit TxGraphImpl(DepGraphIndex max_cluster_count, uint64_t max_cluster_size, uint64_t acceptable_iters) noexcept :
         m_max_cluster_count(max_cluster_count),
         m_max_cluster_size(max_cluster_size),
+        m_acceptable_iters(acceptable_iters),
         m_main_chunkindex(ChunkOrder(this))
     {
         Assume(max_cluster_count >= 1);
@@ -1671,7 +1674,7 @@ uint64_t TxGraphImpl::MakeAcceptable(Cluster& cluster) noexcept
     uint64_t cost{0};
     // Relinearize the Cluster if needed.
     if (!cluster.NeedsSplitting() && !cluster.IsAcceptable() && !cluster.IsOversized()) {
-        cost += cluster.Relinearize(*this, 10000);
+        cost += cluster.Relinearize(*this, m_acceptable_iters);
     }
     return cost;
 }
@@ -2896,7 +2899,7 @@ TxGraph::Ref::Ref(Ref&& other) noexcept
     std::swap(m_index, other.m_index);
 }
 
-std::unique_ptr<TxGraph> MakeTxGraph(unsigned max_cluster_count, uint64_t max_cluster_size) noexcept
+std::unique_ptr<TxGraph> MakeTxGraph(unsigned max_cluster_count, uint64_t max_cluster_size, uint64_t acceptable_iters) noexcept
 {
-    return std::make_unique<TxGraphImpl>(max_cluster_count, max_cluster_size);
+    return std::make_unique<TxGraphImpl>(max_cluster_count, max_cluster_size, acceptable_iters);
 }

src/txgraph.h

@@ -247,7 +247,8 @@ public:
 
 /** Construct a new TxGraph with the specified limit on transactions within a cluster, and the
  *  specified limit on the sum of transaction sizes within a cluster. max_cluster_count cannot
- *  exceed MAX_CLUSTER_COUNT_LIMIT. */
+ *  exceed MAX_CLUSTER_COUNT_LIMIT. acceptable_iters controls how many linearization optimization
-std::unique_ptr<TxGraph> MakeTxGraph(unsigned max_cluster_count, uint64_t max_cluster_size) noexcept;
+ *  steps will be performed before it is considered to be of acceptable quality. */
+std::unique_ptr<TxGraph> MakeTxGraph(unsigned max_cluster_count, uint64_t max_cluster_size, uint64_t acceptable_iters) noexcept;
 
 #endif // BITCOIN_TXGRAPH_H