feat(blobstream): utilizes sdk.Dec type for power difference calculat…

…ion (backport #2719) (#2735)

This is an automatic backport of pull request #2719 done by
[Mergify](https://mergify.com).
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On branch mergify/bp/v1.x/pr-2719
Your branch is up to date with 'origin/v1.x'.

You are currently cherry-picking commit 6192a5a.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   x/qgb/abci.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   x/qgb/types/types_test.go
	both modified:   x/qgb/types/validator.go

```


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</details>

---------

Co-authored-by: Sanaz Taheri <[email protected]>
Co-authored-by: CHAMI Rachid <[email protected]>

x/qgb/abci.go

@@ -12,11 +12,6 @@ import (
 )
 
 const (
-	// SignificantPowerDifferenceThreshold is the threshold of change in the
-	// validator set power that would trigger the creation of a new valset
-	// request.
-	SignificantPowerDifferenceThreshold = 0.05
-
 	oneDay  = 24 * time.Hour
 	oneWeek = 7 * oneDay
 	// AttestationExpiryTime is the expiration time of an attestation. When this
@@ -25,6 +20,11 @@ const (
 	AttestationExpiryTime = 3 * oneWeek // 3 weeks
 )
 
+// SignificantPowerDifferenceThreshold is the threshold of change in the
+// validator set power that would trigger the creation of a new valset
+// request.
+var SignificantPowerDifferenceThreshold = sdk.NewDecWithPrec(5, 2) // 0.05
+
 // EndBlocker is called at the end of every block.
 func EndBlocker(ctx sdk.Context, k keeper.Keeper) {
 	// we always want to create the valset at first so that if there is a new
@@ -117,7 +117,8 @@ func handleValsetRequest(ctx sdk.Context, k keeper.Keeper) {
 			panic(sdkerrors.Wrap(err, "invalid latest valset members"))
 		}
 
-		significantPowerDiff = intCurrMembers.PowerDiff(*intLatestMembers) > SignificantPowerDifferenceThreshold
+		significantPowerDiff = intCurrMembers.PowerDiff(*intLatestMembers).GT(SignificantPowerDifferenceThreshold)
+
 	}
 
 	if (latestValset == nil) || (latestUnbondingHeight == uint64(ctx.BlockHeight())) || significantPowerDiff {

x/qgb/types/types_test.go

@@ -5,6 +5,8 @@ import (
 	mrand "math/rand"
 	"testing"
 
+	sdk "github.com/cosmos/cosmos-sdk/types"
+
 	"github.com/celestiaorg/celestia-app/x/qgb/types"
 	gethcommon "github.com/ethereum/go-ethereum/common"
 	"github.com/stretchr/testify/assert"
@@ -14,7 +16,7 @@ func TestValsetPowerDiff(t *testing.T) {
 	specs := map[string]struct {
 		start types.BridgeValidators
 		diff  types.BridgeValidators
-		exp   float64
+		exp   sdk.Dec
 	}{
 		"no diff": {
 			start: types.BridgeValidators{
@@ -27,7 +29,7 @@ func TestValsetPowerDiff(t *testing.T) {
 				{Power: 2, EvmAddress: "0x8E91960d704Df3fF24ECAb78AB9df1B5D9144140"},
 				{Power: 3, EvmAddress: "0xF14879a175A2F1cEFC7c616f35b6d9c2b0Fd8326"},
 			},
-			exp: 0.0,
+			exp: sdk.NewDecWithPrec(0, 1), // 0.0
 		},
 		"one": {
 			start: types.BridgeValidators{
@@ -40,7 +42,7 @@ func TestValsetPowerDiff(t *testing.T) {
 				{Power: 858993459, EvmAddress: "0x8E91960d704Df3fF24ECAb78AB9df1B5D9144140"},
 				{Power: 2576980377, EvmAddress: "0xF14879a175A2F1cEFC7c616f35b6d9c2b0Fd8326"},
 			},
-			exp: 0.2,
+			exp: sdk.NewDecWithPrec(2, 1), // 0.2
 		},
 		"real world": {
 			start: types.BridgeValidators{
@@ -63,14 +65,16 @@ func TestValsetPowerDiff(t *testing.T) {
 				{Power: 291759231, EvmAddress: "0xF14879a175A2F1cEFC7c616f35b6d9c2b0Fd8326"},
 				{Power: 6785098, EvmAddress: "0x37A0603dA2ff6377E5C7f75698dabA8EE4Ba97B8"},
 			},
-			exp: 0.010000000011641532,
+			exp: sdk.NewDecWithPrec(10000000011641532, 18), // 0.010000000011641532
 		},
 	}
+
 	for msg, spec := range specs {
 		t.Run(msg, func(t *testing.T) {
 			startInternal, _ := spec.start.ToInternal()
 			diffInternal, _ := spec.diff.ToInternal()
-			assert.Equal(t, spec.exp, startInternal.PowerDiff(*diffInternal))
+			obtained := startInternal.PowerDiff(*diffInternal)
+			assert.True(t, spec.exp.Equal(obtained))
 		})
 	}
 }

x/qgb/types/validator.go

@@ -2,9 +2,12 @@ package types
 
 import (
 	"bytes"
-	math "math"
+	"math"
+	"math/big"
 	"sort"
 
+	sdk "github.com/cosmos/cosmos-sdk/types"
+
 	"github.com/ethereum/go-ethereum/common"
 
 	"cosmossdk.io/errors"
@@ -32,7 +35,7 @@ func (b BridgeValidators) ToInternal() (*InternalBridgeValidators, error) {
 	return &ret, nil
 }
 
-// Bridge Validator but with validated EVMAddress.
+// InternalBridgeValidator bridges Validator but with validated EVMAddress.
 type InternalBridgeValidator struct {
 	Power      uint64
 	EVMAddress common.Address
@@ -112,30 +115,35 @@ func EVMAddrLessThan(e common.Address, o common.Address) bool {
 // increases by 1% due to inflation, we shouldn't have to generate a new
 // validator set, after all the validators retained their relative percentages
 // during inflation and normalized QGB power shows no difference.
-func (ibv InternalBridgeValidators) PowerDiff(c InternalBridgeValidators) float64 {
-	powers := map[string]int64{}
+func (ibv InternalBridgeValidators) PowerDiff(c InternalBridgeValidators) sdk.Dec {
+	powers := map[string]sdk.Dec{}
 	// loop over ibv and initialize the map with their powers
 	for _, bv := range ibv {
-		powers[bv.EVMAddress.Hex()] = int64(bv.Power)
+		powers[bv.EVMAddress.Hex()] = sdk.NewDecFromBigInt(new(big.Int).SetUint64(bv.Power))
 	}
 
 	// subtract c powers from powers in the map, initializing
 	// uninitialized keys with negative numbers
 	for _, bv := range c {
+		bvPower := sdk.NewDecFromBigInt(new(big.Int).SetUint64(bv.Power))
 		if val, ok := powers[bv.EVMAddress.Hex()]; ok {
-			powers[bv.EVMAddress.Hex()] = val - int64(bv.Power)
+			powers[bv.EVMAddress.Hex()] = val.Sub(bvPower)
 		} else {
-			powers[bv.EVMAddress.Hex()] = -int64(bv.Power)
+			powers[bv.EVMAddress.Hex()] = bvPower.Neg() // -int64(bv.Power)
 		}
 	}
 
-	var delta float64
+	delta := sdk.NewDec(0)
 	for _, v := range powers {
 		// NOTE: we care about the absolute value of the changes
-		delta += math.Abs(float64(v))
+		v = v.Abs()
+		delta = delta.Add(v)
 	}
 
-	return math.Abs(delta / float64(math.MaxUint32))
+	decMaxUint32 := sdk.NewDec(math.MaxUint32)
+	q := delta.Quo(decMaxUint32)
+
+	return q.Abs()
 }
 
 // TotalPower returns the total power in the bridge validator set.