def test_target_calculation(self):
# see: https://github.com/lbryio/lbrycrd/blob/master/src/test/lbry_tests.cpp
# 1 test block 1 difficulty, should be a max retarget
self.assertEqual(
0x1f00e146,
Headers(':memory').get_next_block_target(
max_target=ArithUint256(Headers.max_target),
previous={
'timestamp': 1386475638
},
current={
'timestamp': 1386475638,
'bits': 0x1f00ffff
}).compact)
# test max retarget (difficulty increase)
self.assertEqual(
0x1f008ccc,
Headers(':memory').get_next_block_target(
max_target=ArithUint256(Headers.max_target),
previous={
'timestamp': 1386475638
},
current={
'timestamp': 1386475638,
'bits': 0x1f00a000
}).compact)
# test min retarget (difficulty decrease)
self.assertEqual(
0x1f00f000,
Headers(':memory').get_next_block_target(
max_target=ArithUint256(Headers.max_target),
previous={
'timestamp': 1386475638
},
current={
'timestamp': 1386475638 + 60 * 20,
'bits': 0x1f00a000
}).compact)
# test to see if pow limit is not exceeded
self.assertEqual(
0x1f00ffff,
Headers(':memory').get_next_block_target(
max_target=ArithUint256(Headers.max_target),
previous={
'timestamp': 1386475638
},
current={
'timestamp': 1386475638 + 600,
'bits': 0x1f00ffff
}).compact)
def get_next_block_target(self, max_target: ArithUint256, previous: Optional[dict],
current: Optional[dict]) -> ArithUint256:
# https://github.com/lbryio/lbrycrd/blob/master/src/lbry.cpp
if previous is None and current is None:
return max_target
if previous is None:
previous = current
actual_timespan = current['timestamp'] - previous['timestamp']
modulated_timespan = self.target_timespan + int((actual_timespan - self.target_timespan) / 8)
minimum_timespan = self.target_timespan - int(self.target_timespan / 8) # 150 - 18 = 132
maximum_timespan = self.target_timespan + int(self.target_timespan / 2) # 150 + 75 = 225
clamped_timespan = max(minimum_timespan, min(modulated_timespan, maximum_timespan))
target = ArithUint256.from_compact(current['bits'])
new_target = min(max_target, (target * clamped_timespan) / self.target_timespan)
return new_target
def get_proof_of_work(cls, header_hash: bytes):
return ArithUint256(int(b'0x' + cls.header_hash_to_pow_hash(header_hash), 16))
def get_next_chunk_target(self, chunk: int) -> ArithUint256:
return ArithUint256(self.max_target)