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Correctly apply penalty bounds on the per-amount penalties

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When we attempt to score a channel which has a success probability
very low, we may have a log well above our cut-off of two. For the
liquidity penalties this works great, we bound it by
`NEGATIVE_LOG10_UPPER_BOUND` and `min` the two scores. For the
amount liquidity penalty we didn't do any `min`ing at all.

This fix is to min the log itself first and then reuse the min'd
log in both calculations.
This commit is contained in:
Matt Corallo 2023-04-10 22:54:48 +00:00
parent 86976e0003
commit c4947acaec
1 changed files with 7 additions and 7 deletions
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14
lightning/src/routing/scoring.rs
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@ -1123,15 +1123,15 @@ impl<L: Deref<Target = u64>, BRT: Deref<Target = HistoricalBucketRangeTracker>,
/// Computes the liquidity penalty from the penalty multipliers.
#[inline(always)]
fn combined_penalty_msat(amount_msat: u64, negative_log10_times_2048: u64,
fn combined_penalty_msat(amount_msat: u64, mut negative_log10_times_2048: u64,
liquidity_penalty_multiplier_msat: u64, liquidity_penalty_amount_multiplier_msat: u64,
) -> u64 {
let liquidity_penalty_msat = {
// Upper bound the liquidity penalty to ensure some channel is selected.
let multiplier_msat = liquidity_penalty_multiplier_msat;
let max_penalty_msat = multiplier_msat.saturating_mul(NEGATIVE_LOG10_UPPER_BOUND);
(negative_log10_times_2048.saturating_mul(multiplier_msat) / 2048).min(max_penalty_msat)
};
negative_log10_times_2048 =
negative_log10_times_2048.min(NEGATIVE_LOG10_UPPER_BOUND * 2048);
// Upper bound the liquidity penalty to ensure some channel is selected.
let liquidity_penalty_msat = negative_log10_times_2048
.saturating_mul(liquidity_penalty_multiplier_msat) / 2048;
let amount_penalty_msat = negative_log10_times_2048
.saturating_mul(liquidity_penalty_amount_multiplier_msat)
.saturating_mul(amount_msat) / 2048 / AMOUNT_PENALTY_DIVISOR;