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Refactor CreateAuctionsFromDeposit (#589)
* refactor CreateAuctionsFromDeposit to complete exhibits 7 & 8 by removing auction slices and simplify usage of largest remainder method
This commit is contained in:
Nick DeLuca
GitHub
parent
db2b237e1d
commit
f0e73e4aa8
@ -30,36 +30,80 @@ func (k Keeper) AuctionCollateral(ctx sdk.Context, deposits types.Deposits, debt
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// CreateAuctionsFromDeposit creates auctions from the input deposit
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func (k Keeper) CreateAuctionsFromDeposit(
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ctx sdk.Context, collateral sdk.Coin, returnAddr sdk.AccAddress, debt, auctionSize sdk.Int,
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principalDenom string) (err error) {
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principalDenom string) error {
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// the number of auctions to start with lot = auctionSize
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wholeAuctions := collateral.Amount.Quo(auctionSize)
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// remaining collateral (< lot) to auction
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partialAuctionAmount := collateral.Amount.Mod(auctionSize)
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auctionLots := []sdk.Int{}
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// number of auctions of auctionSize
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numberOfAuctions := collateral.Amount.Quo(auctionSize)
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debtPerAuction := debt.Mul(auctionSize).Quo(collateral.Amount)
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for i := int64(0); i < wholeAuctions.Int64(); i++ {
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auctionLots = append(auctionLots, auctionSize)
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// last auction for remaining collateral (collateral < auctionSize)
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lastAuctionCollateral := collateral.Amount.Mod(auctionSize)
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lastAuctionDebt := debt.Mul(lastAuctionCollateral).Quo(collateral.Amount)
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// amount of debt that has not been allocated due to
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// rounding error (unallocated debt is less than numberOfAuctions + 1)
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unallocatedDebt := debt.Sub(numberOfAuctions.Mul(debtPerAuction).Add(lastAuctionDebt))
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// rounding error for whole and last auctions in units of collateral
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// higher value means a larger truncation
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wholeAuctionError := debt.Mul(auctionSize).Mod(collateral.Amount)
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lastAuctionError := debt.Mul(lastAuctionCollateral).Mod(collateral.Amount)
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// if last auction has larger rounding error, then allocate one debt to last auction first
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// follows the largest remainder method https://en.wikipedia.org/wiki/Largest_remainder_method
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if lastAuctionError.GT(wholeAuctionError) {
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lastAuctionDebt = lastAuctionDebt.Add(sdk.OneInt())
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unallocatedDebt = unallocatedDebt.Sub(sdk.OneInt())
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}
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if partialAuctionAmount.IsPositive() {
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auctionLots = append(auctionLots, partialAuctionAmount)
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}
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// use the auction lots as weights to split the debt into buckets,
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// where each bucket represents how much debt that auction will attempt to cover
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debtAmounts := splitIntIntoWeightedBuckets(debt, auctionLots)
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debtDenom := k.GetDebtDenom(ctx)
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for i, debtAmount := range debtAmounts {
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numAuctions := numberOfAuctions.Int64()
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// create whole auctions
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for i := int64(0); i < numAuctions; i++ {
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debtAmount := debtPerAuction
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// distribute unallocated debt left over starting with first auction created
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if unallocatedDebt.IsPositive() {
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debtAmount = debtAmount.Add(sdk.OneInt())
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unallocatedDebt = unallocatedDebt.Sub(sdk.OneInt())
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}
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penalty := k.ApplyLiquidationPenalty(ctx, collateral.Denom, debtAmount)
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_, err := k.auctionKeeper.StartCollateralAuction(
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ctx, types.LiquidatorMacc, sdk.NewCoin(collateral.Denom, auctionLots[i]),
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ctx, types.LiquidatorMacc, sdk.NewCoin(collateral.Denom, auctionSize),
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sdk.NewCoin(principalDenom, debtAmount.Add(penalty)), []sdk.AccAddress{returnAddr},
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[]sdk.Int{auctionLots[i]}, sdk.NewCoin(debtDenom, debtAmount),
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[]sdk.Int{auctionSize}, sdk.NewCoin(debtDenom, debtAmount),
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)
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if err != nil {
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return err
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}
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}
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return nil
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// skip last auction if there is no collateral left to auction
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if !lastAuctionCollateral.IsPositive() {
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return nil
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}
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// if the last auction had a larger rounding error than whole auctions,
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// then unallocatedDebt will be zero since we will have already distributed
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// all of the unallocated debt
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if unallocatedDebt.IsPositive() {
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lastAuctionDebt = lastAuctionDebt.Add(sdk.OneInt())
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unallocatedDebt = unallocatedDebt.Sub(sdk.OneInt())
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}
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penalty := k.ApplyLiquidationPenalty(ctx, collateral.Denom, lastAuctionDebt)
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_, err := k.auctionKeeper.StartCollateralAuction(
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ctx, types.LiquidatorMacc, sdk.NewCoin(collateral.Denom, lastAuctionCollateral),
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sdk.NewCoin(principalDenom, lastAuctionDebt.Add(penalty)), []sdk.AccAddress{returnAddr},
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[]sdk.Int{lastAuctionCollateral}, sdk.NewCoin(debtDenom, lastAuctionDebt),
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)
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return err
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}
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// NetSurplusAndDebt burns surplus and debt coins equal to the minimum of surplus and debt balances held by the liquidator module account
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@ -1,81 +0,0 @@
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package keeper
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import (
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"sort"
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sdk "github.com/cosmos/cosmos-sdk/types"
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)
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// splitIntIntoWeightedBuckets divides an initial +ve integer among several buckets in proportion to the buckets' weights
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// It uses the largest remainder method: https://en.wikipedia.org/wiki/Largest_remainder_method
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// See also: https://stackoverflow.com/questions/13483430/how-to-make-rounded-percentages-add-up-to-100
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// note - copied from auction, tests are located there.
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func splitIntIntoWeightedBuckets(amount sdk.Int, buckets []sdk.Int) []sdk.Int {
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// Limit input to +ve numbers as algorithm hasn't been scoped to work with -ve numbers.
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if amount.IsNegative() {
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panic("negative amount")
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}
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if len(buckets) < 1 {
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panic("no buckets")
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}
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for _, bucket := range buckets {
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if bucket.IsNegative() {
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panic("negative bucket")
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}
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}
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// 1) Split the amount by weights, recording whole number part and remainder
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totalWeights := totalInts(buckets...)
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if !totalWeights.IsPositive() {
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panic("total weights must sum to > 0")
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}
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quotients := make([]quoRem, len(buckets))
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for i := range buckets {
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// amount * ( weight/total_weight )
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q := amount.Mul(buckets[i]).Quo(totalWeights)
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r := amount.Mul(buckets[i]).Mod(totalWeights)
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quotients[i] = quoRem{index: i, quo: q, rem: r}
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}
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// 2) Calculate total left over from remainders, and apportion it to buckets with the highest remainder (to minimize error)
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// sort by decreasing remainder order
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sort.Slice(quotients, func(i, j int) bool {
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return quotients[i].rem.GT(quotients[j].rem)
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})
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// calculate total left over from remainders
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allocated := sdk.ZeroInt()
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for _, qr := range quotients {
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allocated = allocated.Add(qr.quo)
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}
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leftToAllocate := amount.Sub(allocated)
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// apportion according to largest remainder
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results := make([]sdk.Int, len(quotients))
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for _, qr := range quotients {
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results[qr.index] = qr.quo
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if !leftToAllocate.IsZero() {
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results[qr.index] = results[qr.index].Add(sdk.OneInt())
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leftToAllocate = leftToAllocate.Sub(sdk.OneInt())
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}
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}
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return results
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}
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type quoRem struct {
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index int
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quo sdk.Int
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rem sdk.Int
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}
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// totalInts adds together sdk.Ints
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func totalInts(is ...sdk.Int) sdk.Int {
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total := sdk.ZeroInt()
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for _, i := range is {
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total = total.Add(i)
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}
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return total
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}
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