413 lines
18 KiB
Python
413 lines
18 KiB
Python
from __future__ import annotations
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from typing import List, Optional, Tuple
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from chia.consensus.block_record import BlockRecord
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from chia.consensus.blockchain_interface import BlockchainInterface
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from chia.consensus.constants import ConsensusConstants
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from chia.types.blockchain_format.sized_bytes import bytes32
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from chia.util.ints import uint8, uint32, uint64, uint128
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from chia.util.significant_bits import count_significant_bits, truncate_to_significant_bits
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def _get_blocks_at_height(
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blocks: BlockchainInterface,
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prev_b: BlockRecord,
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target_height: uint32,
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max_num_blocks: uint32 = uint32(1),
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) -> List[BlockRecord]:
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"""
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Return a consecutive list of BlockRecords starting at target_height, returning a maximum of
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max_num_blocks. Assumes all block records are present. Does a slot linear search, if the blocks are not
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in the path of the peak. Can only fetch ancestors of prev_b.
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Args:
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blocks: dict from header hash to BlockRecord.
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prev_b: prev_b (to start backwards search).
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target_height: target block to start
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max_num_blocks: max number of blocks to fetch (although less might be fetched)
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"""
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if blocks.contains_height(prev_b.height):
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header_hash = blocks.height_to_hash(prev_b.height)
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if header_hash == prev_b.header_hash:
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# Efficient fetching, since we are fetching ancestor blocks within the heaviest chain. We can directly
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# use the height_to_block_record method
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block_list: List[BlockRecord] = []
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for h in range(target_height, target_height + max_num_blocks):
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assert blocks.contains_height(uint32(h))
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block_list.append(blocks.height_to_block_record(uint32(h)))
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return block_list
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# Slow fetching, goes back one by one, since we are in a fork
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curr_b: BlockRecord = prev_b
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target_blocks = []
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while curr_b.height >= target_height:
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if curr_b.height < target_height + max_num_blocks:
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target_blocks.append(curr_b)
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if curr_b.height == 0:
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break
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curr_b = blocks.block_record(curr_b.prev_hash)
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return list(reversed(target_blocks))
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def _get_second_to_last_transaction_block_in_previous_epoch(
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constants: ConsensusConstants,
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blocks: BlockchainInterface,
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last_b: BlockRecord,
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) -> BlockRecord:
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"""
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Retrieves the second to last transaction block in the previous epoch.
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Args:
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constants: consensus constants being used for this chain
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blocks: dict from header hash to block of all relevant blocks
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last_b: last-block in the current epoch, or last block we have seen, if potentially finishing epoch soon
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prev epoch surpassed prev epoch started epoch sur. epoch started
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v v v v
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|.B...B....B. B....B...|......B....B.....B...B.|.B.B.B..|..B...B.B.B...|.B.B.B. B.|........
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PREV EPOCH CURR EPOCH NEW EPOCH
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The blocks selected for the timestamps are the second to last transaction blocks in each epoch.
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Block at height 0 is an exception. Note that H mod EPOCH_BLOCKS where H is the height of the first block in the
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epoch, must be >= 0, and < 128.
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"""
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# This height is guaranteed to be in the next epoch (even when last_b is not actually the last block)
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height_in_next_epoch = (
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last_b.height + 2 * constants.MAX_SUB_SLOT_BLOCKS + constants.MIN_BLOCKS_PER_CHALLENGE_BLOCK + 5
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)
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height_epoch_surpass: uint32 = uint32(height_in_next_epoch - (height_in_next_epoch % constants.EPOCH_BLOCKS))
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height_prev_epoch_surpass: uint32 = uint32(height_epoch_surpass - constants.EPOCH_BLOCKS)
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assert height_prev_epoch_surpass % constants.EPOCH_BLOCKS == height_prev_epoch_surpass % constants.EPOCH_BLOCKS == 0
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# Sanity check, don't go too far past epoch barrier
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assert (height_in_next_epoch - height_epoch_surpass) < (5 * constants.MAX_SUB_SLOT_BLOCKS)
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if height_prev_epoch_surpass == 0:
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# The genesis block is an edge case, where we measure from the first block in epoch (height 0), as opposed to
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# a block in the previous epoch, which would be height < 0
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return _get_blocks_at_height(blocks, last_b, uint32(0))[0]
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# If the prev slot is the first slot, the iterations start at 0
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# We will compute the timestamps of the 2nd to last block in epoch, as well as the total iterations at infusion
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prev_slot_start_iters: uint128
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prev_slot_time_start: uint64
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# The target block must be in this range. Either the surpass block must be a transaction block, or something
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# in it's sub slot must be a transaction block. If that is the only transaction block in the sub-slot, the last
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# block in the previous sub-slot from that must also be a transaction block (therefore -1 is used).
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# The max height for the new epoch to start is surpass + 2*MAX_SUB_SLOT_BLOCKS + MIN_BLOCKS_PER_CHALLENGE_BLOCK - 3,
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# since we might have a deficit > 0 when surpass is hit. The +3 is added just in case
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fetched_blocks = _get_blocks_at_height(
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blocks,
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last_b,
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uint32(height_prev_epoch_surpass - constants.MAX_SUB_SLOT_BLOCKS - 1),
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uint32(3 * constants.MAX_SUB_SLOT_BLOCKS + constants.MIN_BLOCKS_PER_CHALLENGE_BLOCK + 3),
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)
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# We want to find the last block in the slot at which we surpass the height.
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# The last block in epoch will be before this.
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fetched_index: int = constants.MAX_SUB_SLOT_BLOCKS
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curr_b: BlockRecord = fetched_blocks[fetched_index]
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fetched_index += 1
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assert curr_b.height == height_prev_epoch_surpass - 1
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next_b: BlockRecord = fetched_blocks[fetched_index]
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assert next_b.height == height_prev_epoch_surpass
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# Wait until the slot finishes with a challenge chain infusion at start of slot
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# Note that there are no overflow blocks at the start of new epochs
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while next_b.sub_epoch_summary_included is None:
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curr_b = next_b
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next_b = fetched_blocks[fetched_index]
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fetched_index += 1
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# Backtrack to find the second to last tx block
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found_tx_block = 1 if curr_b.is_transaction_block else 0
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while found_tx_block < 2:
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curr_b = blocks.block_record(curr_b.prev_hash)
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if curr_b.is_transaction_block:
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found_tx_block += 1
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return curr_b
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def height_can_be_first_in_epoch(constants: ConsensusConstants, height: uint32) -> bool:
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return (height - (height % constants.SUB_EPOCH_BLOCKS)) % constants.EPOCH_BLOCKS == 0
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def can_finish_sub_and_full_epoch(
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constants: ConsensusConstants,
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blocks: BlockchainInterface,
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height: uint32,
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prev_header_hash: Optional[bytes32],
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deficit: uint8,
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block_at_height_included_ses: bool,
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) -> Tuple[bool, bool]:
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"""
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Returns a bool tuple
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first bool is true if the next sub-slot after height will form part of a new sub-epoch. Therefore
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block height is the last block, and height + 1 is in a new sub-epoch.
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second bool is true if the next sub-slot after height will form part of a new sub-epoch and epoch.
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Therefore, block height is the last block, and height + 1 is in a new epoch.
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Args:
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constants: consensus constants being used for this chain
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blocks: dictionary from header hash to SBR of all included SBR
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height: block height of the (potentially) last block in the sub-epoch
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prev_header_hash: prev_header hash of the block at height, assuming not genesis
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deficit: deficit of block at height height
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block_at_height_included_ses: whether or not the block at height height already included a SES
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"""
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if height < constants.SUB_EPOCH_BLOCKS - 1:
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return False, False
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assert prev_header_hash is not None
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if deficit > 0:
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return False, False
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if block_at_height_included_ses:
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# If we just included a sub_epoch_summary, we cannot include one again
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return False, False
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# This does not check the two edge cases where (height + 1) % constants.SUB_EPOCH_BLOCKS is 0 or 1
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# If it's 0, height+1 is the first place that a sub-epoch can be included
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# If it's 1, we just checked whether 0 included it in the previous check
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if (height + 1) % constants.SUB_EPOCH_BLOCKS > 1:
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curr: BlockRecord = blocks.block_record(prev_header_hash)
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while curr.height % constants.SUB_EPOCH_BLOCKS > 0:
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if curr.sub_epoch_summary_included is not None:
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return False, False
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curr = blocks.block_record(curr.prev_hash)
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if curr.sub_epoch_summary_included is not None:
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return False, False
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# For checking new epoch, make sure the epoch blocks are aligned
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return True, height_can_be_first_in_epoch(constants, uint32(height + 1))
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def _get_next_sub_slot_iters(
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constants: ConsensusConstants,
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blocks: BlockchainInterface,
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prev_header_hash: bytes32,
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height: uint32,
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curr_sub_slot_iters: uint64,
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deficit: uint8,
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block_at_height_included_ses: bool,
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new_slot: bool,
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signage_point_total_iters: uint128,
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skip_epoch_check: bool = False,
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) -> uint64:
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"""
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Returns the slot iterations required for the next block after the one at height, where new_slot is true
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iff the next block will be in the next slot. WARNING: assumes that the block at height is not the first block
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in a sub-epoch.
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Args:
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constants: consensus constants being used for this chain
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blocks: dictionary from header hash to SBR of all included SBR
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prev_header_hash: header hash of the previous block
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height: the block height of the block to look at
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curr_sub_slot_iters: sub-slot iters at the infusion point of the block at height
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deficit: deficit of block at height height
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new_slot: whether or not there is a new slot after height
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signage_point_total_iters: signage point iters of the block at height
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skip_epoch_check: don't check correct epoch
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"""
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next_height: uint32 = uint32(height + 1)
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if next_height < constants.EPOCH_BLOCKS:
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return uint64(constants.SUB_SLOT_ITERS_STARTING)
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if not blocks.contains_block(prev_header_hash):
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raise ValueError(f"Header hash {prev_header_hash} not in blocks")
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prev_b: BlockRecord = blocks.block_record(prev_header_hash)
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# If we are in the same epoch, return same ssi
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if not skip_epoch_check:
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_, can_finish_epoch = can_finish_sub_and_full_epoch(
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constants, blocks, height, prev_header_hash, deficit, block_at_height_included_ses
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)
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if not new_slot or not can_finish_epoch:
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return curr_sub_slot_iters
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last_block_prev: BlockRecord = _get_second_to_last_transaction_block_in_previous_epoch(constants, blocks, prev_b)
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# This gets the last transaction block before this block's signage point. Assuming the block at height height
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# is the last block infused in the epoch: If this block ends up being a
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# transaction block, then last_block_curr will be the second to last tx block in the epoch. If this block
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# is not a transaction block, that means there was exactly one other tx block included in between our signage
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# point and infusion point, and therefore last_block_curr is the second to last as well.
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last_block_curr = prev_b
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while last_block_curr.total_iters > signage_point_total_iters or not last_block_curr.is_transaction_block:
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last_block_curr = blocks.block_record(last_block_curr.prev_hash)
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assert last_block_curr.timestamp is not None and last_block_prev.timestamp is not None
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# This is computed as the iterations per second in last epoch, times the target number of seconds per slot
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new_ssi_precise: uint64 = uint64(
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constants.SUB_SLOT_TIME_TARGET
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* (last_block_curr.total_iters - last_block_prev.total_iters)
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// (last_block_curr.timestamp - last_block_prev.timestamp)
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)
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# Only change by a max factor as a sanity check
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max_ssi = uint64(constants.DIFFICULTY_CHANGE_MAX_FACTOR * last_block_curr.sub_slot_iters)
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min_ssi = uint64(last_block_curr.sub_slot_iters // constants.DIFFICULTY_CHANGE_MAX_FACTOR)
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if new_ssi_precise >= last_block_curr.sub_slot_iters:
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new_ssi_precise = uint64(min(new_ssi_precise, max_ssi))
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else:
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new_ssi_precise = uint64(max([constants.NUM_SPS_SUB_SLOT, new_ssi_precise, min_ssi]))
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new_ssi = truncate_to_significant_bits(new_ssi_precise, constants.SIGNIFICANT_BITS)
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new_ssi = uint64(new_ssi - new_ssi % constants.NUM_SPS_SUB_SLOT) # Must divide the sub slot
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assert count_significant_bits(new_ssi) <= constants.SIGNIFICANT_BITS
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return new_ssi
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def _get_next_difficulty(
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constants: ConsensusConstants,
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blocks: BlockchainInterface,
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prev_header_hash: bytes32,
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height: uint32,
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current_difficulty: uint64,
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deficit: uint8,
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block_at_height_included_ses: bool,
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new_slot: bool,
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signage_point_total_iters: uint128,
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skip_epoch_check: bool = False,
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) -> uint64:
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"""
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Returns the difficulty of the next block that extends onto block.
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Used to calculate the number of iterations. WARNING: assumes that the block at height is not the first block
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in a sub-epoch.
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Args:
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constants: consensus constants being used for this chain
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blocks: dictionary from header hash to SBR of all included SBR
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prev_header_hash: header hash of the previous block
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height: the block height of the block to look at
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deficit: deficit of block at height height
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current_difficulty: difficulty at the infusion point of the block at height
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new_slot: whether or not there is a new slot after height
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signage_point_total_iters: signage point iters of the block at height
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skip_epoch_check: don't check correct epoch
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"""
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next_height: uint32 = uint32(height + 1)
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if next_height < (constants.EPOCH_BLOCKS - 3 * constants.MAX_SUB_SLOT_BLOCKS):
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# We are in the first epoch
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return uint64(constants.DIFFICULTY_STARTING)
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if not blocks.contains_block(prev_header_hash):
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raise ValueError(f"Header hash {prev_header_hash} not in blocks")
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prev_b: BlockRecord = blocks.block_record(prev_header_hash)
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# If we are in the same slot as previous block, return same difficulty
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if not skip_epoch_check:
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_, can_finish_epoch = can_finish_sub_and_full_epoch(
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constants, blocks, height, prev_header_hash, deficit, block_at_height_included_ses
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)
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if not new_slot or not can_finish_epoch:
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return current_difficulty
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last_block_prev: BlockRecord = _get_second_to_last_transaction_block_in_previous_epoch(constants, blocks, prev_b)
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# This gets the last transaction block before this block's signage point. Assuming the block at height height
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# is the last block infused in the epoch: If this block ends up being a
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# transaction block, then last_block_curr will be the second to last tx block in the epoch. If this block
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# is not a transaction block, that means there was exactly one other tx block included in between our signage
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# point and infusion point, and therefore last_block_curr is the second to last as well.
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last_block_curr = prev_b
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while last_block_curr.total_iters > signage_point_total_iters or not last_block_curr.is_transaction_block:
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last_block_curr = blocks.block_record(last_block_curr.prev_hash)
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assert last_block_curr.timestamp is not None
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assert last_block_prev.timestamp is not None
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actual_epoch_time: uint64 = uint64(last_block_curr.timestamp - last_block_prev.timestamp)
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old_difficulty = uint64(prev_b.weight - blocks.block_record(prev_b.prev_hash).weight)
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# Terms are rearranged so there is only one division.
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new_difficulty_precise = uint64(
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(last_block_curr.weight - last_block_prev.weight)
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* constants.SUB_SLOT_TIME_TARGET
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// (constants.SLOT_BLOCKS_TARGET * actual_epoch_time)
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)
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# Only change by a max factor, to prevent attacks, as in greenpaper, and must be at least 1
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max_diff = uint64(constants.DIFFICULTY_CHANGE_MAX_FACTOR * old_difficulty)
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min_diff = uint64(old_difficulty // constants.DIFFICULTY_CHANGE_MAX_FACTOR)
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if new_difficulty_precise >= old_difficulty:
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new_difficulty_precise = uint64(min(new_difficulty_precise, max_diff))
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else:
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new_difficulty_precise = uint64(max([uint64(1), new_difficulty_precise, min_diff]))
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new_difficulty = truncate_to_significant_bits(new_difficulty_precise, constants.SIGNIFICANT_BITS)
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assert count_significant_bits(new_difficulty) <= constants.SIGNIFICANT_BITS
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return uint64(new_difficulty)
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def get_next_sub_slot_iters_and_difficulty(
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constants: ConsensusConstants,
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is_first_in_sub_slot: bool,
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prev_b: Optional[BlockRecord],
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blocks: BlockchainInterface,
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) -> Tuple[uint64, uint64]:
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"""
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Retrieves the current sub_slot iters and difficulty of the next block after prev_b.
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Args:
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constants: consensus constants being used for this chain
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is_first_in_sub_slot: Whether the next block is the first in the sub slot
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prev_b: the previous block (last block in the epoch)
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blocks: dictionary from header hash to SBR of all included SBR
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"""
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# genesis
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if prev_b is None:
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return constants.SUB_SLOT_ITERS_STARTING, constants.DIFFICULTY_STARTING
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if prev_b.height != 0:
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prev_difficulty: uint64 = uint64(prev_b.weight - blocks.block_record(prev_b.prev_hash).weight)
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else:
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# prev block is genesis
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prev_difficulty = uint64(prev_b.weight)
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if prev_b.sub_epoch_summary_included is not None:
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return prev_b.sub_slot_iters, prev_difficulty
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sp_total_iters = prev_b.sp_total_iters(constants)
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difficulty: uint64 = _get_next_difficulty(
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constants,
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blocks,
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prev_b.prev_hash,
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prev_b.height,
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prev_difficulty,
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prev_b.deficit,
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False, # Already checked above
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is_first_in_sub_slot,
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sp_total_iters,
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)
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sub_slot_iters: uint64 = _get_next_sub_slot_iters(
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constants,
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blocks,
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prev_b.prev_hash,
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prev_b.height,
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prev_b.sub_slot_iters,
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prev_b.deficit,
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False, # Already checked above
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is_first_in_sub_slot,
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sp_total_iters,
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)
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return sub_slot_iters, difficulty
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