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Fix precision-related bugs in TidalProtocol calculations #26

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Merged
sisyphusSmiling merged 1 commit into from
Jul 14, 2025
Merged

Fix precision-related bugs in TidalProtocol calculations #26

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41 changes: 32 additions & 9 deletions cadence/contracts/TidalProtocol.cdc
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Original file line number Diff line number Diff line change
Expand Up @@ -255,10 +255,10 @@ access(all) contract TidalProtocol {
/// The total debit balance of the related Token across the whole Pool in which this TokenState resides
access(all) var totalDebitBalance: UInt256
/// The index of the credit interest for the related token. Interest on a token is stored as an "index" which
/// can be thought of as “how many actual tokens does 1 unit of scaled balance represent right now?”
/// can be thought of as "how many actual tokens does 1 unit of scaled balance represent right now?"
access(all) var creditInterestIndex: UInt64
/// The index of the debit interest for the related token. Interest on a token is stored as an "index" which
/// can be thought of as “how many actual tokens does 1 unit of scaled balance represent right now?”
/// can be thought of as "how many actual tokens does 1 unit of scaled balance represent right now?"
access(all) var debitInterestIndex: UInt64
/// The interest rate for credit of the associated token
access(all) var currentCreditRate: UInt64
Expand Down Expand Up @@ -639,11 +639,17 @@ access(all) contract TidalProtocol {
)
let debtEffectiveValue = TidalProtocolUtils.div(TidalProtocolUtils.mul(uintDepositPrice, trueDebt), uintDepositBorrowFactor)

// Ensure we don't underflow - if debtEffectiveValue is greater than effectiveDebtAfterWithdrawal,
// it means we can pay off all debt
var effectiveDebtAfterPayment: UInt256 = 0
if debtEffectiveValue <= effectiveDebtAfterWithdrawal {
effectiveDebtAfterPayment = effectiveDebtAfterWithdrawal - debtEffectiveValue
}

// Check what the new health would be if we paid off all of this debt
let potentialHealth = TidalProtocol.healthComputation(
effectiveCollateral: effectiveCollateralAfterWithdrawal,
effectiveDebt: effectiveDebtAfterWithdrawal - debtEffectiveValue
effectiveDebt: effectiveDebtAfterPayment
)

// Does paying off all of the debt reach the target health? Then we're done.
Expand All @@ -652,8 +658,8 @@ access(all) contract TidalProtocol {
// compute how many units of the token would be needed to reach the target health.
let healthChange = targetHealth - healthAfterWithdrawal
// let requiredEffectiveDebt = effectiveDebtAfterWithdrawal - effectiveCollateralAfterWithdrawal / targetHealth
let requiredEffectiveDebt = TidalProtocolUtils.div(
effectiveDebtAfterWithdrawal - effectiveCollateralAfterWithdrawal,
let requiredEffectiveDebt = effectiveDebtAfterWithdrawal - TidalProtocolUtils.div(
effectiveCollateralAfterWithdrawal,
TidalProtocolUtils.ufix64ToUInt256(targetHealth, decimals: TidalProtocolUtils.decimals)
)

Expand All @@ -671,7 +677,12 @@ access(all) contract TidalProtocol {
// we have to record the amount of tokens that went towards debt payback and adjust the effective
// debt to reflect that it has been paid off.
debtTokenCount = trueDebt
effectiveDebtAfterWithdrawal = effectiveDebtAfterWithdrawal - debtEffectiveValue
// Ensure we don't underflow
if debtEffectiveValue <= effectiveDebtAfterWithdrawal {
effectiveDebtAfterWithdrawal = effectiveDebtAfterWithdrawal - debtEffectiveValue
} else {
effectiveDebtAfterWithdrawal = 0
}
healthAfterWithdrawal = potentialHealth
}
}
Expand Down Expand Up @@ -1153,6 +1164,16 @@ access(all) contract TidalProtocol {
}

if !canWithdraw {
// Log detailed information about the failed withdrawal
let availableBalance = self.availableBalance(pid: pid, type: type, pullFromTopUpSource: false)
log(" [CONTRACT] WITHDRAWAL FAILED:")
log(" [CONTRACT] Position ID: \(pid)")
log(" [CONTRACT] Token type: \(type.identifier)")
log(" [CONTRACT] Requested amount: \(amount)")
log(" [CONTRACT] Available balance (without topUp): \(availableBalance)")
log(" [CONTRACT] Required deposit for minHealth: \(requiredDeposit)")
log(" [CONTRACT] Pull from topUpSource: \(pullFromTopUpSource)")

// We can't service this withdrawal, so we just abort
panic("Cannot withdraw \(amount) of \(type.identifier) from position ID \(pid) - Insufficient funds for withdrawal")
}
Expand Down Expand Up @@ -1810,10 +1831,12 @@ access(all) contract TidalProtocol {
}

/// A multiplication function for interest calculations. It assumes that both values are very close to 1 and
/// represent fixed point numbers with 16 decimal places of precision.
/// represent fixed point numbers with 18 decimal places of precision.
access(all) view fun interestMul(_ a: UInt64, _ b: UInt64): UInt64 {
let aScaled = a / UInt64(TidalProtocolUtils.e8)
let bScaled = b / UInt64(TidalProtocolUtils.e8)
// For 18-decimal precision, we need to divide by e9 (not e8)
// This is because: (a/1e9) * (b/1e9) = (a*b)/1e18
let aScaled = a / 1_000_000_000 // 10^9
let bScaled = b / 1_000_000_000 // 10^9
Comment on lines +1838 to +1839
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@sisyphusSmiling sisyphusSmiling Jul 14, 2025

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We should update TidalProtocolUtils.e8 to e9 = 1_000_000_000


return aScaled * bScaled
}
Expand Down
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