def add(self, block: Block) -> bool:
log("BLOCKCHAIN {} ADDING {}".format(self, block))
if block.difficulty < self.difficulty:
log("BLOCKCHAIN {} REJECT {} TOO LIGHT {} < {}".format(self, block, block.difficulty, self.difficulty))
return False
if block.previous.id != self.tip.id:
if block.previous.id in self.blocks:
log("BLOCKCHAIN {} REJECT {} STALE".format(self, block))
else:
log("BLOCKCHAIN {} REJECT {} UNKNOWN TIP {}".format(self, block, block.previous.id))
return False
log("BLOCKCHAIN {} ACCEPT {}".format(self, block))
self.blocks[block.id] = block
self.heights.append(block.id)
self.height += 1
self.weight += block.difficulty
# if self.height % self.difficulty_readjustment_period == 0:
# self.readjust_difficulty()
return True
def readjust_difficulty(self):
#
# By construction,
#
# old_difficulty new_difficulty
# ------------------- = observed hashrate = -----------------
# observed block time target block time
#
# so new_difficulty = (target block time * old_difficulty) / (observed block time)
#
log("BLOCKCHAIN {} DIFF READJ AT BLOCK {}".format(self, self.height))
blocks = [self.blocks[block_id] for block_id in list(reversed(self.heights))[:self.difficulty_readjustment_period]]
block_gaps = [(blocks[index+1].time - block.time) for index, block in enumerate(blocks[:-1])]
observed_block_time = mean(block_gaps)
old_difficulty = self.difficulty
new_difficulty = (self.block_time * old_difficulty) / observed_block_time
difficulty_change_ratio = new_difficulty / old_difficulty
if difficulty_change_ratio > self.max_difficulty_change_factor:
difficulty_change_ratio = self.max_difficulty_change_factor
elif difficulty_change_ratio < self.inverse_max_difficulty_change_factor:
difficulty_change_ratio = self.inverse_max_difficulty_change_factor
self.difficulty = old_difficulty * difficulty_change_ratio
log("BLOCKCHAIN {} DIFF. ADJ. {} => {}".format(self, old_difficulty, self.difficulty))
def merge(self, other: 'Blockchain') -> bool:
log("BLOCKCHAIN {} MERGING {}".format(self, other))
assert other.chain_params == self.chain_params
if other.weight < self.weight:
log("BLOCKCHAIN {} REJECT {} AS LIGHTER CHAIN".format(self, other))
return False
log("BLOCKCHAIN {} ACCEPT {}".format(self, other))
self.blocks = {block_id:block for (block_id, block) in other.blocks.items()}
self.heights = [block_id for block_id in other.heights]
self.height = other.height
self.weight = other.weight
self.difficulty = other.difficulty
return True
def receive(self, time, transmission):
log("AGENT {} RECEIVE {}".format(self.id, transmission.id))
self.transmissions_received[time] = transmission
def log_advance(self, duration):
log("AGENT {} ADVANCE w/ {}".format(self.id, [
transmission.id
for transmission in self.transmissions_received.values()
]))