Function checkCalculatedDifficulty

src/cpp-ethereum/test/libethcore/difficulty.cpp:44–102

)";

void checkCalculatedDifficulty(BlockHeader const& _bi, BlockHeader const& _parent, Network _n, ChainOperationParams const& _p, string const& _testName = "")
{
	u256 difficulty = _bi.difficulty();
	u256 frontierDiff = _p.u256Param("homsteadForkBlock");

	//The ultimate formula (Homestead)
	if (_bi.number() > frontierDiff)
	{
		u256 minimumDifficulty = _p.u256Param("minimumDifficulty");
		bigint block_diff = _parent.difficulty();

		bigint a = (_parent.difficulty() / 2048);
		int b = 1 - int(_bi.timestamp() - _parent.timestamp()) / 10;
		bigint c = (_bi.number() / 100000) - 2;

		block_diff += a * max<int>(b, -99);
		block_diff += u256(1) << (unsigned)c;
		block_diff = max<bigint>(minimumDifficulty, block_diff);

		BOOST_CHECK_MESSAGE(difficulty == block_diff, "Homestead Check Calculated diff = " << difficulty << " expected diff = " << block_diff << _testName);
		return;
	}

	u256 durationLimit;
	u256 minimumDifficulty;
	u256 difficultyBoundDivisor;
	switch(_n)
	{
	case Network::MainNetwork:
	case Network::FrontierTest:
	case Network::HomesteadTest:
	case Network::Ropsten:
	case Network::TransitionnetTest:
		durationLimit = 13;
		minimumDifficulty = 131072;
		difficultyBoundDivisor = 2048;
	break;
	default:
		cerr << "testing undefined network difficulty";
		durationLimit = _p.u256Param("durationLimit");
		minimumDifficulty = _p.u256Param("minimumDifficulty");
		difficultyBoundDivisor = _p.u256Param("difficultyBoundDivisor");
		break;
	}

	//Frontier Era
	bigint block_diff = _parent.difficulty();

	bigint a = (_parent.difficulty() / difficultyBoundDivisor);
	bigint b = ((_bi.timestamp() - _parent.timestamp()) < durationLimit) ?  1 : -1;
	bigint c = (_bi.number() / 100000) - 2;

	block_diff += a * b;
	block_diff += u256(1) << (unsigned)c;
	block_diff = max<bigint>(minimumDifficulty, block_diff);

	BOOST_CHECK_MESSAGE(difficulty == block_diff, "Check Calculated diff = " << difficulty << " expected diff = " << block_diff << _testName);
	return;