WhitePaperInterestRateModel

Compound's WhitePaperInterestRateModel Contract

The parameterized model described in section 2.4 of the original Compound Protocol whitepaper

Solidity API

multiplierPerBlock

The multiplier of utilization rate that gives the slope of the interest rate

uint256 multiplierPerBlock

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baseRatePerBlock

The base interest rate which is the y-intercept when utilization rate is 0

uint256 baseRatePerBlock

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constructor

Construct an interest rate model

constructor(uint256 baseRatePerYear, uint256 multiplierPerYear) public

Parameters

Name	Type	Description
baseRatePerYear	uint256	The approximate target base APR, as a mantissa (scaled by EXP_SCALE)
multiplierPerYear	uint256	The rate of increase in interest rate wrt utilization (scaled by EXP_SCALE)

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getBorrowRate

Calculates the current borrow rate per block, with the error code expected by the market

function getBorrowRate(uint256 cash, uint256 borrows, uint256 reserves, uint256 badDebt) public view returns (uint256)

Parameters

Name	Type	Description
cash	uint256	The amount of cash in the market
borrows	uint256	The amount of borrows in the market
reserves	uint256	The amount of reserves in the market
badDebt	uint256	The amount of badDebt in the market

Return Values

Name	Type	Description
[0]	uint256	The borrow rate percentage per block as a mantissa (scaled by EXP_SCALE)

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getSupplyRate

Calculates the current supply rate per block

function getSupplyRate(uint256 cash, uint256 borrows, uint256 reserves, uint256 reserveFactorMantissa, uint256 badDebt) public view returns (uint256)

Parameters

Name	Type	Description
cash	uint256	The amount of cash in the market
borrows	uint256	The amount of borrows in the market
reserves	uint256	The amount of reserves in the market
reserveFactorMantissa	uint256	The current reserve factor for the market
badDebt	uint256	The amount of badDebt in the market

Return Values

Name	Type	Description
[0]	uint256	The supply rate percentage per block as a mantissa (scaled by EXP_SCALE)

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utilizationRate

Calculates the utilization rate of the market: (borrows + badDebt) / (cash + borrows + badDebt - reserves)

function utilizationRate(uint256 cash, uint256 borrows, uint256 reserves, uint256 badDebt) public pure returns (uint256)

Parameters

Name	Type	Description
cash	uint256	The amount of cash in the market
borrows	uint256	The amount of borrows in the market
reserves	uint256	The amount of reserves in the market (currently unused)
badDebt	uint256	The amount of badDebt in the market

Return Values

Name	Type	Description
[0]	uint256	The utilization rate as a mantissa between [0, MANTISSA_ONE]

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