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Dynamic base liquidation percentage #539

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Mar 24, 2020
Merged

Dynamic base liquidation percentage #539

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da18fbd
Remove AUCTION_BASE_PERCENTAGE constant
Mar 23, 2020
6f7c1f6
Implement getAuctionBasePercentage
Mar 23, 2020
3b0233b
Expose getInitialCollateralizedPercent for testing
Mar 23, 2020
a91a1e3
test getAuctionBasePercentage
Mar 23, 2020
1ed77a3
Updates tests
Mar 23, 2020
5621289
Track initialCollateralizedPercent
Mar 24, 2020
b46d498
Update Tests
Mar 24, 2020
8ef9c4b
Merge branch 'master' into base-liq-percent
Shadowfiend Mar 24, 2020
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1 change: 1 addition & 0 deletions implementation/contracts/deposit/DepositFunding.sol
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Expand Up @@ -70,6 +70,7 @@ library DepositFunding {
_d.signerFeeDivisor = _system.getSignerFeeDivisor();
_d.undercollateralizedThresholdPercent = _system.getUndercollateralizedThresholdPercent();
_d.severelyUndercollateralizedThresholdPercent = _system.getSeverelyUndercollateralizedThresholdPercent();
_d.initialCollateralizedPercent = _system.getInitialCollateralizedPercent();
_d.signingGroupRequestedAt = block.timestamp;

_d.setAwaitingSignerSetup();
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5 changes: 2 additions & 3 deletions implementation/contracts/deposit/DepositUtils.sol
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Expand Up @@ -33,6 +33,7 @@ library DepositUtils {
uint256 lotSizeSatoshis;
uint8 currentState;
uint256 signerFeeDivisor;
uint128 initialCollateralizedPercent;
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This and the two below seem like they can be smaller than uint128, perhaps? Could even be a uint8? Maybe a uint16 if we want to allow ourselves maximum flexibility, but our percentages are expressed as percentages, so uint8 gives us up to 250% as a representation 🤔

Not sure if the Solidity compiler is good enough to pack things together and save us gas in that case though.

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Uint16 for some peace of mind. Also, the enforced initialCollateralizedPercent max is 300, which is over the 255 uint8 limit.
Solidity will automatically pack where possible, given the variables fit into a single 32-byte increment. two uint128s should be packed

uint128 undercollateralizedThresholdPercent;
uint128 severelyUndercollateralizedThresholdPercent;

Expand Down Expand Up @@ -373,9 +374,7 @@ library DepositUtils {
/// @return The percentage of the InitialCollateralizationPercent that will result
/// in a 100% bond value base auction given perfect collateralization.
function getAuctionBasePercentage(Deposit storage _d) internal view returns (uint256) {
ITBTCSystem _sys = ITBTCSystem(_d.TBTCSystem);
uint256 initialCollateralizedPercent = _sys.getInitialCollateralizedPercent();
return (10000 / initialCollateralizedPercent);
return uint256(10000).div(_d.initialCollateralizedPercent);
}

/// @notice Seize the signer bond from the keep contract.
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4 changes: 4 additions & 0 deletions implementation/contracts/test/deposit/TestDeposit.sol
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Expand Up @@ -73,6 +73,10 @@ contract TestDeposit is Deposit {
self.undercollateralizedThresholdPercent = _undercollateralizedThresholdPercent;
}

function setInitialCollateralizedPercent(uint128 _initialCollateralizedPercent) public {
self.initialCollateralizedPercent = _initialCollateralizedPercent;
}

function getUndercollateralizedThresholdPercent() public view returns (uint128) { return self.undercollateralizedThresholdPercent; }

function setSeverelyUndercollateralizedThresholdPercent(uint128 _severelyUndercollateralizedThresholdPercent) public {
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1 change: 1 addition & 0 deletions implementation/test/DepositLiquidationTest.js
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Expand Up @@ -83,6 +83,7 @@ describe("DepositLiquidation", async function() {

before(async () => {
lotSize = await testDeposit.lotSizeTbtc.call()
await testDeposit.setInitialCollateralizedPercent(new BN(150))
buyer = accounts[1]
})

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6 changes: 3 additions & 3 deletions implementation/test/DepositUtilsTest.js
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Expand Up @@ -389,9 +389,9 @@ describe("DepositUtils", async function() {

const initialCollateralization = await tbtcSystemStub.getInitialCollateralizedPercent()

// 10000 to avoid losing value to truncating is solidity.
const expecged = new BN(10000).div(initialCollateralization)
expect(basePercentage).to.eq.BN(expecged) // 66 for 150
// 10000 to avoid losing value to truncating in solidity.
const expected = new BN(10000).div(initialCollateralization)
expect(basePercentage).to.eq.BN(expected) // 66 for 150
})
})

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