Optimized RNG usage

src/block_template.cpp

@@ -198,9 +198,12 @@ static FORCEINLINE uint64_t get_block_reward(uint64_t base_reward, uint64_t medi
 
 void BlockTemplate::shuffle_tx_order()
 {
-	const int64_t n = static_cast<int64_t>(m_mempoolTxsOrder.size());
-	for (int64_t i = n - 1; i > 0; --i) {
-		std::swap(m_mempoolTxsOrder[i], m_mempoolTxsOrder[m_rng() % (i + 1)]);
+	const uint64_t n = m_mempoolTxsOrder.size();
+	if (n > 1) {
+		for (uint64_t i = 0, k; i < n - 1; ++i) {
+			umul128(m_rng(), n - i, &k);
+			std::swap(m_mempoolTxsOrder[i], m_mempoolTxsOrder[i + k]);
+		}
 	}
 }
 
@@ -636,7 +639,7 @@ void BlockTemplate::update(const MinerData& data, const Mempool& mempool, Wallet
 	uint32_t* sidechain_extra = m_poolBlockTemplate->m_sidechainExtraBuf;
 	sidechain_extra[0] = 0;
 	sidechain_extra[1] = (P2POOL_VERSION_MAJOR << 16) | P2POOL_VERSION_MINOR;
-	sidechain_extra[2] = static_cast<uint32_t>(m_rng());
+	sidechain_extra[2] = static_cast<uint32_t>(m_rng() >> 32);
 	sidechain_extra[3] = 0;
 
 	m_poolBlockTemplate->m_nonce = 0;

src/stratum_server.cpp

@@ -60,14 +60,14 @@ StratumServer::StratumServer(p2pool* pool)
 	// Diffuse the initial state in case it has low quality
 	m_rng.discard(10000);
 
-	m_extraNonce = PoolBlock::signal_v2_readiness(static_cast<uint32_t>(m_rng()));
-
 	m_hashrateData[0] = { seconds_since_epoch(), 0 };
 
 	uv_mutex_init_checked(&m_blobsQueueLock);
 	uv_mutex_init_checked(&m_rngLock);
 	uv_rwlock_init_checked(&m_hashrateDataLock);
 
+	m_extraNonce = PoolBlock::signal_v2_readiness(get_random32());
+
 	m_submittedSharesPool.resize(10);
 	for (size_t i = 0; i < m_submittedSharesPool.size(); ++i) {
 		m_submittedSharesPool[i] = new SubmittedShare{};
@@ -107,7 +107,7 @@ void StratumServer::on_block(const BlockTemplate& block)
 		return;
 	}
 
-	const uint32_t extra_nonce_start = PoolBlock::signal_v2_readiness(static_cast<uint32_t>(get_random64()));
+	const uint32_t extra_nonce_start = PoolBlock::signal_v2_readiness(get_random32());
 	m_extraNonce.exchange(extra_nonce_start + num_connections);
 
 	BlobsData* blobs_data = new BlobsData{};
@@ -283,7 +283,7 @@ bool StratumServer::on_login(StratumClient* client, uint32_t id, const char* log
 		[client, id, &hashing_blob, job_id, blob_size, target, height, &seed_hash](void* buf, size_t buf_size)
 		{
 			do {
-				client->m_rpcId = static_cast<uint32_t>(static_cast<StratumServer*>(client->m_owner)->get_random64());
+				client->m_rpcId = static_cast<StratumServer*>(client->m_owner)->get_random32();
 			} while (!client->m_rpcId);
 
 			log::hex_buf target_hex(reinterpret_cast<const uint8_t*>(&target), sizeof(uint64_t));
@@ -463,10 +463,10 @@ bool StratumServer::on_submit(StratumClient* client, uint32_t id, const char* jo
 	return result;
 }
 
-uint64_t StratumServer::get_random64()
+uint32_t StratumServer::get_random32()
 {
 	MutexLock lock(m_rngLock);
-	return m_rng();
+	return static_cast<uint32_t>(m_rng() >> 32);
 }
 
 void StratumServer::print_status()

src/stratum_server.h

@@ -84,7 +84,7 @@ public:
 
 	bool on_login(StratumClient* client, uint32_t id, const char* login);
 	bool on_submit(StratumClient* client, uint32_t id, const char* job_id_str, const char* nonce_str, const char* result_str);
-	uint64_t get_random64();
+	uint32_t get_random32();
 
 	void print_status() override;
 	void show_workers();