Avoid div by zero.

Always prepare work, even when not apparently mining.

eth/main.cpp

@@ -379,8 +379,8 @@ void doFarm(MinerType _m, string const& _remote, unsigned _recheckPeriod)
 				{
 					current.headerHash = hh;
 					current.seedHash = h256(v[1].asString());
-					current.boundary = h256(v[2].asString());
-					cnote << "Got new work package.";
+					current.boundary = h256(fromHex(v[2].asString()), h256::AlignRight);
+					cnote << "Got work package:" << current.headerHash.abridged() << " < " << current.boundary;
 					f.setWork(current);
 				}
 				this_thread::sleep_for(chrono::milliseconds(_recheckPeriod));
@@ -395,7 +395,7 @@ void doFarm(MinerType _m, string const& _remote, unsigned _recheckPeriod)
 		}
 		catch (jsonrpc::JsonRpcException&)
 		{
-			for (auto i = 10; --i; this_thread::sleep_for(chrono::seconds(1)))
+			for (auto i = 3; --i; this_thread::sleep_for(chrono::seconds(1)))
 				cerr << "JSON-RPC problem. Probably couldn't connect. Retrying in " << i << "... \r";
 			cerr << endl;
 		}

libethcore/BlockInfo.cpp

@@ -77,7 +77,7 @@ h256 const& BlockInfo::hash() const
 
 h256 const& BlockInfo::boundary() const
 {
-	if (!m_boundary)
+	if (!m_boundary && difficulty)
 		m_boundary = (h256)(u256)((bigint(1) << 256) / difficulty);
 	return m_boundary;
 }

libethcore/Miner.h

@@ -24,7 +24,9 @@
 #include <thread>
 #include <list>
 #include <atomic>
+#include <boost/timer.hpp>
 #include <libdevcore/Common.h>
+#include <libdevcore/Log.h>
 #include <libdevcore/Worker.h>
 #include <libethcore/Common.h>
 
@@ -105,8 +107,12 @@ public:
 		}
 		if (!!_work)
 		{
+			boost::timer t;
 			pause();
+			cdebug << "pause took" << t.elapsed();
+			t.restart();
 			kickOff();
+			cdebug << "kickOff took" << t.elapsed();
 		}
 		else if (!_work && !!old)
 			pause();

libethereum/Client.cpp

@@ -530,15 +530,15 @@ void Client::onChainChanged(ImportRoute const& _ir)
 void Client::onPostStateChanged()
 {
 	cnote << "Post state changed: Restarting mining...";
-	if (isMining())
-	{
+//	if (isMining())
+//	{
 		{
 			WriteGuard l(x_postMine);
 			m_postMine.commitToMine(m_bc);
 			m_miningInfo = m_postMine.info();
 		}
 		m_farm.setWork(m_miningInfo);
-	}
+//	}
 	m_remoteWorking = false;
 }