ensurePrecomputed should respect --no-precompute

libethcore/Ethash.cpp

@@ -212,6 +212,8 @@ std::string Ethash::name()
 	return "Ethash";
 }
 
+bool Ethash::s_precompute = false;
+
 unsigned Ethash::revision()
 {
 	return ETHASH_REVISION;
@@ -219,7 +221,7 @@ unsigned Ethash::revision()
 
 void Ethash::ensurePrecomputed(unsigned _number)
 {
-	if (_number % ETHASH_EPOCH_LENGTH > ETHASH_EPOCH_LENGTH * 9 / 10)
+	if (s_precompute && _number % ETHASH_EPOCH_LENGTH > ETHASH_EPOCH_LENGTH * 9 / 10)
 		// 90% of the way to the new epoch
 		EthashAux::computeFull(EthashAux::seedHash(_number + ETHASH_EPOCH_LENGTH), true);
 }

libethcore/Ethash.h

@@ -49,12 +49,14 @@ class EthashCLHook;
 class Ethash
 {
 public:
+	static bool s_precompute;
 	static std::string name();
 	static unsigned revision();
 	static SealEngineFace* createSealEngine();
 
 	using Nonce = h64;
 
+	static void setPrecompute(bool _shouldPrecompute) { s_precompute = _shouldPrecompute; }
 	static void manuallySubmitWork(SealEngineFace* _engine, h256 const& _mixHash, Nonce _nonce);
 	static bool isWorking(SealEngineFace* _engine);
 	static WorkingProgress workingProgress(SealEngineFace* _engine);