# Precision loss due to engines not using .muldiv() when calculating lp ratios Low/Info · Three Sigma · Hybrid orderbook DEX · 3rd April 2024 Finding 3S-Vertex-L04 of the Vertex security review. - Report: /reports/vertex - Source: https://github.com/0xsimao/audits/blob/main/Three%20Sigma/2024-04-03-vertex.pdf --- ### Description For example, in SpotEngineState::_getInLpBalance(), the [ratio](https://github.com/vertex-protocol/vertex-contracts-3sigma-audit/blob/main/contracts/SpotEngineState.sol#L338) is calculated first, likely incurring in precision loss as lpState.supply is expected to be bigger than 1e18 (used in .div()). This means that baseAmount and quoteAmount will be smaller due to the precision loss. ### Recommendation Everytime a division and multiplication are to be applied and division loss could occur (when the denominator is bigger than 1e18), [mulDiv()](https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/math/Math.sol#L128) should be used. https://github.com/vertex-protocol/vertex-contracts-3sigma-audit/blob/main/contracts/SpotEngineLP.sol#L38 https://github.com/vertex-protocol/vertex-contracts-3sigma-audit/blob/main/contracts/PerpEngineState.sol#L115 https://github.com/vertex-protocol/vertex-contracts-3sigma-audit/blob/main/contracts/PerpEngine.sol#L174 https://github.com/vertex-protocol/vertex-contracts-3sigma-audit/blob/main/contracts/PerpEngine.sol#L177 ### Status Acknowledged Disclosed by 0xSimao (https://0xsimao.com/). --- Related findings: - [WBTCZapper precision loss will lead to reverts](https://0xsimao.com/findings/evro-finance-ii-wbtc-zapper-precision-reverts): Evro Collateral Onboarding - [Precision Loss in `notifyRewardAmount` Function Causes Unclaimable RewardToken](https://0xsimao.com/findings/exactly-protocol-update-staking-contract-ii-precision-notify-reward-unclaimable): Exactly Protocol Update - Staking Contract - [Multiplication after division in StableEarnerRateModel leads to loss of precision](https://0xsimao.com/findings/m-0-stable-earner-model-precision): M^0 Minter Gateway