DEV-7. Balance pool: optimizations, redundant logic removed. ValidDelta bug fix

[Bromel777]

Optimizations

To optimize cpu and memory costs of the swap action validation in the main PBalancePool.hs contract we made the following changes:

• The value of the constant pDen is reduced from 10 to 5 to decrease number of exponentiations and required number of significant figures in the values ​​of the involved state variables;
• The length of variable values ​​is now pre-calculated off-chain and checked for correctness inside the pool contract using the checkLength function, main additions here are:
  • An invariantLength field is added into the BalancePoolConfig to explicitly pass the number of significant figures of the invariant value;
  • A lengths field is added the BalancePoolRedeemer to explicitly pass the number of significant figures of the pool's state variables and off-chain calculated values, namely: gXgYLength, newXBalanceLength, newGXLength, newTxPowLength, newTxPowWeightLength, leftSideLengthX, rightSideLengthX, newYBalanceLength, newGYLength, newTyPowLength, newTyPowWeightLength, leftSideLengthY, rightSideLengthY;
  • Implemented a more efficient exponentiation function pow10 for calculating exponents with pre-known power values, i.e. calculated from lengths.

Bug fixes

• The validDelta predicate inside the verifyTExpEquality function is now calculated taking into account the error from rounding calculations (in consistency with newInvariantIsCorrect, correctTokenError and validGEquality predicates).
• Verification of the valid invariant value is added into the validDepositRedeemAllTokens function to prevent a possible break of the pool due to an incorrect invariant value saved in the datum after malicious redeem/deposit actions.

[linear]

DEV-7 Weighted pool contracts (Balancer)

Weighted math - easy read

Balancer white paper** - hard read**

[Bromel777]

waiting audit complete before merge