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chore: add OZ rounding up in sqrt #78

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May 1, 2025
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chore: add OZ rounding up in sqrt #78

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8 changes: 3 additions & 5 deletions src/libraries/CurveLib.sol
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Original file line number Diff line number Diff line change
Expand Up @@ -68,16 +68,14 @@ library CurveLib {
unchecked {
squaredB = absB * absB; // scale: 1e36
discriminant = squaredB + fourAC; // scale: 1e36
sqrt = Math.sqrt(discriminant); // scale: 1e18
sqrt = (sqrt * sqrt < discriminant) ? sqrt + 1 : sqrt;
sqrt = Math.sqrt(discriminant, Math.Rounding.Ceil); // scale: 1e18
}
} else {
// B^2 cannot be calculated directly at 1e18 scale without overflowing
uint256 scale = computeScale(absB); // calculate the scaling factor such that B^2 can be calculated without overflowing
squaredB = Math.mulDiv(absB / scale, absB, scale, Math.Rounding.Ceil);
discriminant = squaredB + fourAC / (scale * scale);
sqrt = Math.sqrt(discriminant);
sqrt = (sqrt * sqrt < discriminant) ? sqrt + 1 : sqrt;
sqrt = Math.sqrt(discriminant, Math.Rounding.Ceil);
sqrt = sqrt * scale;
}

Expand All @@ -86,7 +84,7 @@ library CurveLib {
// use the regular quadratic formula solution (-b + sqrt(b^2 - 4ac)) / 2a
x = Math.mulDiv(absB + sqrt, 1e18, 2 * c, Math.Rounding.Ceil) + 1;
} else {
// use the "citardauq" quadratic formula solution 2c / (-b + sqrt(b^2 - 4ac))
// use the "citardauq" quadratic formula solution 2c / (-b - sqrt(b^2 - 4ac))
x = (2 * C + (absB + sqrt - 1)) / (absB + sqrt) + 1;
}

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