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[WIP] Fix the satisfaction algorithm to include non-canon sats #26

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[WIP] Fix the satisfaction algorithm to include non-canon sats #26

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34 changes: 25 additions & 9 deletions bip380/miniscript/fragments.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@
See the Miniscript website for the specification of the type system: https://bitcoin.sipa.be/miniscript/.
"""

import copy
import bip380.miniscript.parsing as parsing

from bip380.key import DescriptorKey
Expand Down Expand Up @@ -45,7 +44,7 @@

from .errors import MiniscriptNodeCreationError
from .property import Property
from .satisfaction import ExecutionInfo, Satisfaction
from .satisfaction import ExecutionInfo, Satisfaction, ThreshSubsInfo


# Threshold for nLockTime: below this value it is interpreted as block number,
Expand Down Expand Up @@ -88,7 +87,8 @@ class Node:
# Whether this node does not contain a mix of timelock or heightlock of different types.
# That is, not (abs_heightlocks and rel_heightlocks or abs_timelocks and abs_timelocks)
no_timelock_mix = None
# Information about this Miniscript execution (satisfaction cost, etc..)
# Information about this Miniscript execution (satisfaction cost, etc..). Note that the
# execution information assumes non-malleable satisfaction.
exec_info = None

def __init__(self, *args, **kwargs):
Expand Down Expand Up @@ -511,7 +511,7 @@ def satisfaction(self, sat_material):
return Satisfaction.from_concat(sat_material, *self.subs)

def dissatisfaction(self):
return Satisfaction.unavailable() # it's V.
return (self.subs[1].dissatisfy() + self.subs[0].satisfy()).set_non_canon()

def __repr__(self):
return f"and_v({','.join(map(str, self.subs))})"
Expand Down Expand Up @@ -564,7 +564,15 @@ def satisfaction(self, sat_material):
return Satisfaction.from_concat(sat_material, self.subs[0], self.subs[1])

def dissatisfaction(self):
return self.subs[1].dissatisfaction() + self.subs[0].dissatisfaction()
return (
(self.subs[1].dissatisfaction() + self.subs[0].dissatisfaction())
| (
self.subs[1].dissatisfaction() + self.subs[0].satisfaction()
).set_non_canon()
| (
self.subs[1].satisfaction() + self.subs[0].dissatisfaction()
).set_non_canon()
)

def __repr__(self):
return f"and_b({','.join(map(str, self.subs))})"
Expand Down Expand Up @@ -854,8 +862,10 @@ def satisfaction(self, sat_material):
) | (self.subs[2].satisfaction(sat_material) + self.subs[0].dissatisfaction())

def dissatisfaction(self):
# Dissatisfy X and Z
return self.subs[2].dissatisfaction() + self.subs[0].dissatisfaction()
# Dissatisfy X and Z [or satisfy X but dissatisfy Y]
return (self.subs[2].dissatisfaction() + self.subs[0].dissatisfaction()) | (
self.subs[1].dissatisfaction() + self.subs[0].satisfaction()
).set_non_canon()

def __repr__(self):
return f"andor({','.join(map(str, self.subs))})"
Expand Down Expand Up @@ -945,9 +955,10 @@ def satisfaction(self, sat_material):
return Satisfaction.from_thresh(sat_material, self.k, self.subs)

def dissatisfaction(self):
return sum(
all_dissat = sum(
[sub.dissatisfaction() for sub in self.subs], start=Satisfaction(witness=[])
)


def __repr__(self):
return f"thresh({self.k},{','.join(map(str, self.subs))})"
Expand Down Expand Up @@ -1172,7 +1183,12 @@ def exec_info(self):
return ExecutionInfo.from_wrap_dissat(self.sub.exec_info, ops_count=4, dissat=1)

def dissatisfaction(self):
return Satisfaction(witness=[b""])
sub_dissat = self.sub.dissatisfy()
return Satisfaction(witness=[b""]) | (
sub_dissat.non_canon()
if not sub_dissat.is_unavailable() and len(sub_dissat.witness[-1]) > 0
else Satisfaction.unavailable()
)

def __repr__(self):
# Avoid duplicating colons
Expand Down
79 changes: 54 additions & 25 deletions bip380/miniscript/satisfaction.py
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,35 @@ def max_optional(a, b):
return max(a, b)


class ThreshSubsInfo:
"""Information about a thresh fragment's sub-fragments."""

def __init__(self, subs, sat_material):
# Fragments that cannot be satisfied with the given material.
self.unsatisfiable = []
# Fragments that cannot be dis-satisfied with the given material.
self.undissatisfiable = []
# The fragments that are both satisfiable and dis-satisfiable with
# the given material, along with whether they require a signature and
# the difference in size between their satisfaction and dis-satisfaction.
# These are stored inside the list so that it may be sorted to prefer
# satisfying fragments that don't require a signature and have a smaller
# satisfaction.
self.available = []

self.available, self.unsatisfiable, self.undissatisfiable = [], [], []
for sub in subs:
sat, dissat = sub.satisfaction(sat_material), sub.dissatisfaction()
if sat.witness is None:
self.unsatisfiable.append(sub)
elif dissat.witness is None:
self.undissatisfiable.append(sub)
else:
self.available.append(
(int(sat.has_sig), len(sat.witness) - len(dissat.witness), sub)
)


class SatisfactionMaterial:
"""Data that may be needed in order to satisfy a Minsicript fragment."""

Expand Down Expand Up @@ -59,14 +88,11 @@ def __repr__(self):
class Satisfaction:
"""All information about a satisfaction."""

def __init__(self, witness, has_sig=False):
def __init__(self, witness, has_sig=False, non_canon=False):
assert isinstance(witness, list) or witness is None
self.witness = witness
self.has_sig = has_sig
# TODO: we probably need to take into account non-canon sats, as the algorithm
# described on the website mandates it:
# > Iterate over all the valid satisfactions/dissatisfactions in the table above
# > (including the non-canonical ones),
self.non_canon = non_canon

def __add__(self, other):
"""Concatenate two satisfactions together."""
Expand Down Expand Up @@ -114,6 +140,10 @@ def unavailable():
def is_unavailable(self):
return self.witness is None

def set_non_canon(self):
self.non_canon = True
return self

def size(self):
return len(self.witness) + sum(len(elem) for elem in self.witness)

Expand All @@ -126,8 +156,12 @@ def from_concat(sat_material, sub_a, sub_b, disjunction=False):
:param disjunction: Whether this fragment has an 'or()' semantic.
"""
if disjunction:
return (sub_b.dissatisfaction() + sub_a.satisfaction(sat_material)) | (
sub_b.satisfaction(sat_material) + sub_a.dissatisfaction()
return (
(sub_b.dissatisfaction() + sub_a.satisfaction(sat_material))
| (sub_b.satisfaction(sat_material) + sub_a.dissatisfaction())
| (
sub_b.satisfaction(sat_material) + sub_a.satisfaction(sat_material)
).set_non_canon()
)
return sub_b.satisfaction(sat_material) + sub_a.satisfaction(sat_material)

Expand All @@ -150,29 +184,22 @@ def from_thresh(sat_material, k, subs):
:param k: The number of subs that need to be satisfied.
:param subs: The list of all subs of the threshold.
"""
# Pick the k sub-fragments to satisfy, prefering (in order):
# 1. Fragments that don't require a signature to be satisfied
# 2. Fragments whose satisfaction's size is smaller
# Record the unavailable (in either way) ones as we go.
arbitrage, unsatisfiable, undissatisfiable = [], [], []
for sub in subs:
sat, dissat = sub.satisfaction(sat_material), sub.dissatisfaction()
if sat.witness is None:
unsatisfiable.append(sub)
elif dissat.witness is None:
undissatisfiable.append(sub)
else:
arbitrage.append(
(int(sat.has_sig), len(sat.witness) - len(dissat.witness), sub)
)
thresh_info = ThreshSubsInfo(subs, sat_material)

# If not enough (dis)satisfactions are available, fail.
if len(unsatisfiable) > len(subs) - k or len(undissatisfiable) > k:
if (
len(thresh_info.unsatisfiable) > len(subs) - k
or len(thresh_info.undissatisfiable) > k
):
return Satisfaction.unavailable()

# Otherwise, satisfy the k most optimal ones.
arbitrage = sorted(arbitrage, key=lambda x: x[:2])
optimal_sat = undissatisfiable + [a[2] for a in arbitrage] + unsatisfiable
arbitrage = sorted(thresh_info.available, key=lambda x: x[:2])
optimal_sat = (
thresh_info.undissatisfiable
+ [a[2] for a in arbitrage]
+ thresh_info.unsatisfiable
)
to_satisfy = set(optimal_sat[:k])
return sum(
[
Expand Down Expand Up @@ -343,6 +370,8 @@ def from_thresh(k, subs):
# All subs are executed, there is no OP_IF branch.
dyn_ops = sum([sub._dyn_ops_count for sub in subs])

# FIXME: has_sig should be taken into account. Maybe use ThreshSubsInfo.

# In order to estimate the worst case we simulate to satisfy the k subs whose
# sat/dissat ratio is the largest, and dissatisfy the others.
# We do so by iterating through all the subs, recording their sat-dissat "score"
Expand Down