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refactor: check total difficulty with short-circuit
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@yangby-cryptape
yangby-cryptape committed Aug 24, 2023
1 parent ae04578 commit 08bdda9
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Showing 2 changed files with 90 additions and 44 deletions.
107 changes: 70 additions & 37 deletions src/protocols/light_client/components/send_last_state_proof.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -487,16 +487,23 @@ impl EpochDifficultyTrend {
}
}

// Calculate the limit of total difficulty.
pub(crate) fn calculate_total_difficulty_limit(
// Check the limit of total difficulty.
#[allow(clippy::too_many_arguments)]
pub(crate) fn check_total_difficulty_limit(
&self,
start_epoch_difficulty: &U256,
limit: EstimatedLimit,
n: u64,
k: u64,
actual: &U256,
start: &U256,
tau: u64,
details: &EpochDifficultyTrendDetails,
) -> U256 {
let mut curr = start_epoch_difficulty.clone();
unaligned: &U256,
) -> Result<(), String> {
let details = self.split_epochs(limit, n, k).remove_last_epoch();
let mut curr = start.clone();
let mut total = U256::zero();
let tau_u256 = U256::from(tau);
let check_max = matches!(limit, EstimatedLimit::Max);
for group in &[details.start, details.end] {
match group {
EpochCountGroupByTrend::Decreased(epochs_count) => {
Expand All @@ -510,7 +517,20 @@ impl EpochDifficultyTrend {
state: {}, trend: {:?}, details: {:?}",
total, curr, index, epochs_count, tau, state, self, details
);
})
});
if total >= *actual {
if check_max {
debug!("check total difficulty: not greater than upper limit (short-circuit)");
return Ok(());
} else {
let errmsg = format!(
"failed since total difficulty ({actual:#x}) is less than \
the lower limit (short-circuit at {total:#x}) with \
start epoch difficulty {start:#x}, n: {n}, k: {k}"
);
return Err(errmsg);
}
}
}
}
EpochCountGroupByTrend::Increased(epochs_count) => {
Expand All @@ -524,12 +544,45 @@ impl EpochDifficultyTrend {
state: {}, trend: {:?}, details: {:?}",
total, curr, index, epochs_count, tau, state, self, details
);
})
});
if total >= *actual {
if check_max {
debug!("check total difficulty: not greater than upper limit (short-circuit)");
return Ok(());
} else {
let errmsg = format!(
"failed since total difficulty ({actual:#x}) is less than \
the lower limit (short-circuit at {total:#x}) with \
start epoch difficulty {start:#x}, n: {n}, k: {k}"
);
return Err(errmsg);
}
}
}
}
}
}
total
if check_max {
if &total + unaligned >= *actual {
debug!("check total difficulty: not greater than upper limit (fully-calculated)");
Ok(())
} else {
let errmsg = format!(
"failed since total difficulty ({actual:#x}) is greater than the upper limit
({total:#x}+{unaligned:#x}) with start epoch difficulty {start:#x}, n: {n}, k: {k}"
);
Err(errmsg)
}
} else if &total + unaligned <= *actual {
debug!("check total difficulty: not less than lower limit (fully-calculated)");
Ok(())
} else {
let errmsg = format!(
"failed since total difficulty ({actual:#x}) is less than the lower limit
({total:#x}+{unaligned:#x}) with start epoch difficulty {start:#x}, n: {n}, k: {k}"
);
Err(errmsg)
}
}
}

Expand Down Expand Up @@ -962,34 +1015,14 @@ pub(crate) fn verify_total_difficulty(
// `n / 2 >= 1` was checked since the above branch.
let n = epochs_switch_count;
let diff = &start_epoch_difficulty;
let aligned_difficulty_min = {
let details = epoch_difficulty_trend
.split_epochs(EstimatedLimit::Min, n, k)
.remove_last_epoch();
epoch_difficulty_trend.calculate_total_difficulty_limit(diff, tau, &details)
};
let aligned_difficulty_max = {
let details = epoch_difficulty_trend
.split_epochs(EstimatedLimit::Max, n, k)
.remove_last_epoch();
epoch_difficulty_trend.calculate_total_difficulty_limit(diff, tau, &details)
};
let total_difficulity_min = &unaligned_difficulty_calculated + &aligned_difficulty_min;
let total_difficulity_max = &unaligned_difficulty_calculated + &aligned_difficulty_max;
if total_difficulty < total_difficulity_min || total_difficulty > total_difficulity_max
{
let errmsg = format!(
"failed since total difficulty ({:#x}) isn't in the range ({:#x}+[{:#x},{:#x}]) \
during epochs ([{:#},{:#}])",
total_difficulty,
unaligned_difficulty_calculated,
aligned_difficulty_min,
aligned_difficulty_max,
start_epoch,
end_epoch
);
return Err(errmsg);
}
let total = &total_difficulty;
let unaligned = &unaligned_difficulty_calculated;
let limit = EstimatedLimit::Min;
epoch_difficulty_trend
.check_total_difficulty_limit(limit, n, k, total, diff, tau, unaligned)?;
let limit = EstimatedLimit::Max;
epoch_difficulty_trend
.check_total_difficulty_limit(limit, n, k, total, diff, tau, unaligned)?;
}
}

Expand Down
27 changes: 20 additions & 7 deletions src/protocols/light_client/components/tests/send_last_state_proof.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -155,7 +155,7 @@ fn test_split_epochs() {
}

#[test]
fn test_calculate_total_difficulty_limit() {
fn test_check_total_difficulty_limit() {
let tau = 2;
let testcases = [
// Unchanged
Expand All @@ -172,7 +172,16 @@ fn test_calculate_total_difficulty_limit() {
for n in n_min..=(n_min + 10) {
for limit in [EstimatedLimit::Min, EstimatedLimit::Max] {
let details = trend.split_epochs(limit, n, k).remove_last_epoch();
let actual = trend.calculate_total_difficulty_limit(&diff_start, tau, &details);
let unaligned = U256::zero();
let actual = trend.check_total_difficulty_limit(
limit,
n,
k,
&diff_end,
&diff_start,
tau,
&unaligned,
);
let expected = {
let start_epochs_count = details.start.epochs_count();
let end_epochs_count = details.end.epochs_count();
Expand All @@ -188,6 +197,7 @@ fn test_calculate_total_difficulty_limit() {
curr *= tau;
total += &curr;
}
diff_end >= total
}
EstimatedLimit::Max => {
for _ in 0..start_epochs_count {
Expand All @@ -198,15 +208,18 @@ fn test_calculate_total_difficulty_limit() {
curr /= tau;
total += &curr;
}
diff_end <= total
}
}
total
};
assert_eq!(
actual, expected,
"{:#x} -> {:#x} (tau: {}, n: {}, k: {}, {:?}) \
total difficulty expect {:#x} but got {:#x}",
diff_start, diff_end, tau, n, k, limit, expected, actual,
actual.is_ok(),
expected,
"{diff_start:#x} -> {diff_end:#x} (tau: {tau}, n: {n}, k: {k}, {limit:?}) \
total difficulty expect {} but got {} since {}",
expected,
actual.is_ok(),
actual.unwrap_err(),
);
}
}
Expand Down

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