fix(oracle): Remove float SQRT calculation to avoid determinism issues (

#1700) * fix: remove float sqrt calculation * chore: changelog * fix(oracle): exact sqrts (common.SqrtDec) gives more accurate math --------- Co-authored-by: Unique-Divine <[email protected]>
NibiruChain · Dec 11, 2023 · b400eed · b400eed
1 parent f4d0933
commit b400eed
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Showing 3 changed files with 10 additions and 10 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -133,6 +133,7 @@ v0.47.5.
 * [#1614](https://github.com/NibiruChain/nibiru/pull/1614) - refactor(proto): Use explicit namespacing on proto imports for #1608
 * [#1610](https://github.com/NibiruChain/nibiru/pull/1610) - refactor(app): Simplify app.go with less redundant imports using struct embedding.
 * [#1606](https://github.com/NibiruChain/nibiru/pull/1606) - fix(perp): emit `MarketUpdatedEvent` in the absence of index price
+* [#1700](https://github.com/NibiruChain/nibiru/pull/1700) - fix(oracle): remove non deterministic sqrt calculation
 
 ### Dependencies
 

diff --git a/x/oracle/types/ballot.go b/x/oracle/types/ballot.go
@@ -2,13 +2,11 @@ package types
 
 import (
 	"encoding/json"
-	"fmt"
-	"math"
 	"sort"
-	"strconv"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
 
+	"github.com/NibiruChain/nibiru/x/common"
 	"github.com/NibiruChain/nibiru/x/common/asset"
 )
 
@@ -149,9 +147,10 @@ func (pb ExchangeRateVotes) StandardDeviation(median sdk.Dec) (standardDeviation
 
 	variance := sum.QuoInt64(int64(n))
 
-	floatNum, _ := strconv.ParseFloat(variance.String(), 64)
-	floatNum = math.Sqrt(floatNum)
-	standardDeviation, _ = sdk.NewDecFromStr(fmt.Sprintf("%f", floatNum))
+	standardDeviation, err := common.SqrtDec(variance)
+	if err != nil {
+		return sdk.ZeroDec()
+	}
 
 	return
 }

diff --git a/x/oracle/types/ballot_test.go b/x/oracle/types/ballot_test.go
@@ -242,21 +242,21 @@ func TestPBStandardDeviation(t *testing.T) {
 			[]float64{1.0, 2.0, 10.0, 100000.0},
 			[]int64{1, 1, 100, 1},
 			[]bool{true, true, true, true},
-			sdk.NewDecWithPrec(4999500036300, types.OracleDecPrecision),
+			sdk.MustNewDecFromStr("49995.000362536000000000"),
 		},
 		{
 			// Adding fake validator doesn't change outcome
 			[]float64{1.0, 2.0, 10.0, 100000.0, 10000000000},
 			[]int64{1, 1, 100, 1, 10000},
 			[]bool{true, true, true, true, false},
-			sdk.NewDecWithPrec(447213595075100600, types.OracleDecPrecision),
+			sdk.MustNewDecFromStr("4472135950.751005519000000000"),
 		},
 		{
 			// Tie votes
 			[]float64{1.0, 2.0, 3.0, 4.0},
 			[]int64{1, 100, 100, 1},
 			[]bool{true, true, true, true},
-			sdk.NewDecWithPrec(122474500, types.OracleDecPrecision),
+			sdk.MustNewDecFromStr("1.224744871000000000"),
 		},
 		{
 			// No votes
@@ -270,7 +270,7 @@ func TestPBStandardDeviation(t *testing.T) {
 			[]float64{1.0, 2.0, 10.0, 100000.0, -99999999999.0, 0},
 			[]int64{1, 1, 100, 1, 1, 1},
 			[]bool{true, true, true, true, true, true},
-			sdk.NewDecWithPrec(4999500036300, types.OracleDecPrecision),
+			sdk.MustNewDecFromStr("49995.000362536000000000"),
 		},
 	}