[refactor/bench] make mempool_stress bench reusable and parameterizable

Author: glozow

src/bench/mempool_stress.cpp

@@ -26,14 +26,8 @@ struct Available {
     Available(CTransactionRef& ref, size_t tx_count) : ref(ref), tx_count(tx_count){}
 };
 
-static void ComplexMemPool(benchmark::Bench& bench)
+static std::vector<CTransactionRef> CreateOrderedCoins(FastRandomContext& det_rand, int childTxs, int min_ancestors)
 {
-    int childTxs = 800;
-    if (bench.complexityN() > 1) {
-        childTxs = static_cast<int>(bench.complexityN());
-    }
-
-    FastRandomContext det_rand{true};
     std::vector<Available> available_coins;
     std::vector<CTransactionRef> ordered_coins;
     // Create some base transactions
@@ -58,8 +52,10 @@ static void ComplexMemPool(benchmark::Bench& bench)
             size_t idx = det_rand.randrange(available_coins.size());
             Available coin = available_coins[idx];
             uint256 hash = coin.ref->GetHash();
-            // biased towards taking just one ancestor, but maybe more
-            size_t n_to_take = det_rand.randrange(2) == 0 ? 1 : 1+det_rand.randrange(coin.ref->vout.size() - coin.vin_left);
+            // biased towards taking min_ancestors parents, but maybe more
+            size_t n_to_take = det_rand.randrange(2) == 0 ?
+                               min_ancestors :
+                               min_ancestors + det_rand.randrange(coin.ref->vout.size() - coin.vin_left);
             for (size_t i = 0; i < n_to_take; ++i) {
                 tx.vin.emplace_back();
                 tx.vin.back().prevout = COutPoint(hash, coin.vin_left++);
@@ -79,6 +75,17 @@ static void ComplexMemPool(benchmark::Bench& bench)
         ordered_coins.emplace_back(MakeTransactionRef(tx));
         available_coins.emplace_back(ordered_coins.back(), tx_counter++);
     }
+    return ordered_coins;
+}
+
+static void ComplexMemPool(benchmark::Bench& bench)
+{
+    FastRandomContext det_rand{true};
+    int childTxs = 800;
+    if (bench.complexityN() > 1) {
+        childTxs = static_cast<int>(bench.complexityN());
+    }
+    std::vector<CTransactionRef> ordered_coins = CreateOrderedCoins(det_rand, childTxs, /* min_ancestors */ 1);
     const auto testing_setup = MakeNoLogFileContext<const TestingSetup>(CBaseChainParams::MAIN);
     CTxMemPool pool;
     LOCK2(cs_main, pool.cs);