Negative rebase mechanism

Ilya · February 20, 2021, 2:30pm

Please, explain how negative rebase works. Is it like AMPL?
I ask this question becase before last rebase I had 2659 USDx - and now I have zero USDx.
It could be less by X% but how it could became zero?
@Robert ?

Robert · February 20, 2021, 2:48pm

It does not work exactly like ampl - if you look at the code here:

github.com

Dollar-Protocol/protocol/blob/ce31f049d3346eddc7cf74ddd2a908798e9ddafe/contracts/usdx/dollars.sol#L540


function dividendsOwing(address account) public view returns (uint256) {
    if (_totalDividendPoints > Shares.lastDividendPoints(account) && Shares.stakingStatus(account) == 1) {
        uint256 newDividendPoints = _totalDividendPoints.sub(Shares.lastDividendPoints(account));
        uint256 sharesBalance = Shares.externalRawBalanceOf(account);
        return sharesBalance.mul(newDividendPoints).div(POINT_MULTIPLIER);
    } else {
        return 0;
    }
}
function debtOwing(address account) public view returns (uint256) {
    if (_totalDebtPoints > debtPoints[account] && !debaseWhitelist[account]) {
        uint256 newDebtPoints = _totalDebtPoints.sub(debtPoints[account]);
        uint256 dollarBalance = _dollarBalances[account];
        return dollarBalance.mul(newDebtPoints).div(POINT_MULTIPLIER);
    } else {
        return 0;
    }
}
modifier updateAccount(address account) {

Users accrue debt in proportion to the amount the protocol wants to decrease in supply. It is possible for the debt to be greater than the current balance.

I think this is a point for discussion among those technical here as to how best to resolve this.

Ilya · February 20, 2021, 3:19pm

Thanks for your reply!

Could you explain please, how users accrue debt?

Also, here is said that the maximum contraction is 10% of the total USD Supply.
This does not work at all - negativeRebaseHelper function is not used nowadays?

Robert · February 21, 2021, 6:24pm

See that there is a Boolean that when true caps negative rebase to 10% of total supply. Currently that variable is false until turned on by governance.

Joshua · February 24, 2021, 8:38am

This also happened to me recently. Im not sure which rebase it was, but 3-4 days ago sounds about right since I last noticed I had SOME USDx. Though in practice the last interaction I had with DP was to redeem all of my Xbond for USDx, and now I have 0.

Is it possible there’s something else going on here? I’m not particularly knowledgeable about Solidity, so I can forgive that the way this rebasing is written may be for many good reasons, but ideally it shouldnt be taking balances to 0 very often at all right?

Is it possible that there’s a bad actor manipulating some of the nuance here, or perhaps a bug that was introduced around this time? Seems possible that it could have something to do with the whitelisting function or the recent Xbond redemption?