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[audit]#9.1 improve math precision

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mingda
2020-07-10 13:32:20 +08:00
parent 9af81c1bd9
commit 51be40478a
1 changed files with 14 additions and 8 deletions
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22
contracts/lib/DODOMath.sol
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@@ -35,9 +35,8 @@ library DODOMath {
uint256 k
) internal pure returns (uint256) {
uint256 fairAmount = DecimalMath.mul(i, V1.sub(V2)); // i*delta
uint256 V0V1 = DecimalMath.divCeil(V0, V1); // V0/V1
uint256 V0V2 = DecimalMath.divCeil(V0, V2); // V0/V2
uint256 penalty = DecimalMath.mul(DecimalMath.mul(k, V0V1), V0V2); // k(V0^2/V1/V2)
uint256 V0V0V1V2 = DecimalMath.divCeil(V0.mul(V0).div(V1), V2);
uint256 penalty = DecimalMath.mul(k, V0V0V1V2); // k(V0^2/V1/V2)
return DecimalMath.mul(fairAmount, DecimalMath.ONE.sub(k).add(penalty));
}
@@ -70,7 +69,7 @@ library DODOMath {
if (deltaBSig) {
b = b.add(ideltaB); // (1-k)Q1+i*deltaB
} else {
kQ02Q1 = kQ02Q1.add(ideltaB); // -i*(-deltaB)-kQ0^2/Q1
kQ02Q1 = kQ02Q1.add(ideltaB); // i*deltaB+kQ0^2/Q1
}
if (b >= kQ02Q1) {
b = b.sub(kQ02Q1);
@@ -89,10 +88,17 @@ library DODOMath {
// final res
uint256 denominator = DecimalMath.ONE.sub(k).mul(2); // 2(1-k)
uint256 numerator;
if (minusbSig) {
return DecimalMath.divFloor(b.add(squareRoot), denominator);
numerator = b.add(squareRoot);
} else {
return DecimalMath.divFloor(squareRoot.sub(b), denominator);
numerator = squareRoot.sub(b);
}
if (deltaBSig) {
return DecimalMath.divFloor(numerator, denominator);
} else {
return DecimalMath.divCeil(numerator, denominator);
}
}
@@ -108,9 +114,9 @@ library DODOMath {
uint256 fairAmount
) internal pure returns (uint256 V0) {
// V0 = V1+V1*(sqrt-1)/2k
uint256 sqrt = DecimalMath.divFloor(DecimalMath.mul(k, fairAmount).mul(4), V1);
uint256 sqrt = DecimalMath.divCeil(DecimalMath.mul(k, fairAmount).mul(4), V1);
sqrt = sqrt.add(DecimalMath.ONE).mul(DecimalMath.ONE).sqrt();
uint256 premium = DecimalMath.divFloor(sqrt.sub(DecimalMath.ONE), k.mul(2));
uint256 premium = DecimalMath.divCeil(sqrt.sub(DecimalMath.ONE), k.mul(2));
// V0 is greater than or equal to V1 according to the solution
return DecimalMath.mul(V1, DecimalMath.ONE.add(premium));
}