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cryptachia/ghost: update fork choice rule comments

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David Rusu 2024-11-14 16:08:38 +04:00
parent 55da6dd79d
commit dca237fc51
1 changed files with 5 additions and 6 deletions
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11
cryptarchia/cryptarchia.py
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@ -748,7 +748,8 @@ def block_weight(states: Dict[Id, LedgerState]) -> Dict[Id, int]:
return block_weight return block_weight
# Implementation of the fork choice rule as defined in the Ouroboros Genesis paper # Implementation of the Cryptarchia fork choice rule:
# We use a combination of the chain density rule from Ouroboros Genesis and GHOST
# k defines the forking depth of chain we accept without more analysis # k defines the forking depth of chain we accept without more analysis
# s defines the length of time (unit of slots) after the fork happened we will inspect for chain density # s defines the length of time (unit of slots) after the fork happened we will inspect for chain density
def ghost_maxvalid_bg( def ghost_maxvalid_bg(
@ -767,19 +768,17 @@ def ghost_maxvalid_bg(
for fork in forks: for fork in forks:
cmax_depth, fork_depth = common_prefix_depth(cmax, fork, states) cmax_depth, fork_depth = common_prefix_depth(cmax, fork, states)
if cmax_depth <= k: if cmax_depth <= k:
# GHOST fork choice rule: select the branch with most weight at the point of divergence
cmax_divergent_block = chain_suffix(cmax, cmax_depth, states)[0].block.id() cmax_divergent_block = chain_suffix(cmax, cmax_depth, states)[0].block.id()
fork_divergent_block = chain_suffix(fork, fork_depth, states)[0].block.id() fork_divergent_block = chain_suffix(fork, fork_depth, states)[0].block.id()
# Classic longest chain rule with parameter k
if weights[cmax_divergent_block] < weights[fork_divergent_block]: if weights[cmax_divergent_block] < weights[fork_divergent_block]:
cmax = fork cmax = fork
else: else:
# The chain is forking too much, we need to pay a bit more attention # The chain is forking too much, we need to pay a bit more attention
# In particular, select the chain that is the densest after the fork # In particular, select the chain that is the densest after the fork
forking_block = local_chain cmax_divergent_block = chain_suffix(cmax, cmax_depth, states)[0].block
for _ in range(cmax_depth):
forking_block = states[forking_block].block.parent
forking_slot = Slot(states[forking_block].block.slot.absolute_slot + s) forking_slot = Slot(cmax_divergent_block.slot.absolute_slot + s)
cmax_density = chain_density(cmax, forking_slot, cmax_depth, states) cmax_density = chain_density(cmax, forking_slot, cmax_depth, states)
fork_density = chain_density(fork, forking_slot, fork_depth, states) fork_density = chain_density(fork, forking_slot, fork_depth, states)