osmomath: QuoTruncate with no reallocation

CHANGELOG.md

@@ -45,6 +45,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Features
 
 * [#6427](https://github.com/osmosis-labs/osmosis/pull/6427) sdk.Coins Mul and Quo helpers in osmoutils
+* [#6428](https://github.com/osmosis-labs/osmosis/pull/6428) osmomath: QuoTruncateMut
 * [#6437](https://github.com/osmosis-labs/osmosis/pull/6437) mutative version for QuoRoundUp
 
 ### Misc Improvements

osmomath/decimal.go

@@ -387,6 +387,19 @@ func (d BigDec) QuoTruncate(d2 BigDec) BigDec {
 	return BigDec{chopped}
 }
 
+// quotient truncate (mutative)
+func (d BigDec) QuoTruncateMut(d2 BigDec) BigDec {
+	// multiply precision twice
+	d.i.Mul(d.i, squaredPrecisionReuse)
+	d.i.Quo(d.i, d2.i)
+
+	chopPrecisionAndTruncateMut(d.i)
+	if d.i.BitLen() > maxDecBitLen {
+		panic("Int overflow")
+	}
+	return d
+}
+
 // quotient, round up
 func (d BigDec) QuoRoundUp(d2 BigDec) BigDec {
 	// multiply precision twice

osmomath/decimal_test.go

@@ -1560,3 +1560,62 @@ func (s *decimalTestSuite) TestQuoRoundUp_MutativeAndNonMutative() {
 		}
 	}
 }
+
+func (s *decimalTestSuite) TestQuoTruncate_MutativeAndNonMutative() {
+	tests := []struct {
+		d1, d2, expQuoTruncateMut osmomath.BigDec
+	}{
+		{osmomath.NewBigDec(0), osmomath.NewBigDec(0), osmomath.NewBigDec(0)},
+		{osmomath.NewBigDec(1), osmomath.NewBigDec(0), osmomath.NewBigDec(0)},
+		{osmomath.NewBigDec(0), osmomath.NewBigDec(1), osmomath.NewBigDec(0)},
+		{osmomath.NewBigDec(0), osmomath.NewBigDec(-1), osmomath.NewBigDec(0)},
+		{osmomath.NewBigDec(-1), osmomath.NewBigDec(0), osmomath.NewBigDec(0)},
+
+		{osmomath.NewBigDec(1), osmomath.NewBigDec(1), osmomath.NewBigDec(1)},
+		{osmomath.NewBigDec(-1), osmomath.NewBigDec(-1), osmomath.NewBigDec(1)},
+		{osmomath.NewBigDec(1), osmomath.NewBigDec(-1), osmomath.NewBigDec(-1)},
+		{osmomath.NewBigDec(-1), osmomath.NewBigDec(1), osmomath.NewBigDec(-1)},
+
+		{
+			osmomath.NewBigDec(3), osmomath.NewBigDec(7), osmomath.MustNewBigDecFromStr("0.428571428571428571428571428571428571"),
+		},
+		{
+			osmomath.NewBigDec(2), osmomath.NewBigDec(4), osmomath.NewBigDecWithPrec(5, 1),
+		},
+
+		{osmomath.NewBigDec(100), osmomath.NewBigDec(100), osmomath.NewBigDec(1)},
+
+		{
+			osmomath.NewBigDecWithPrec(15, 1), osmomath.NewBigDecWithPrec(15, 1), osmomath.NewBigDec(1),
+		},
+		{
+			osmomath.NewBigDecWithPrec(3333, 4), osmomath.NewBigDecWithPrec(333, 4), osmomath.MustNewBigDecFromStr("10.009009009009009009009009009009009009"),
+		},
+	}
+
+	for tcIndex, tc := range tests {
+		tc := tc
+
+		if tc.d2.IsZero() { // panic for divide by zero
+			s.Require().Panics(func() { tc.d1.QuoTruncateMut(tc.d2) })
+		} else {
+
+			copy := tc.d1.Clone()
+
+			nonMutResult := copy.QuoTruncate(tc.d2)
+
+			// Return is as expected
+			s.Require().Equal(tc.expQuoTruncateMut, nonMutResult, "exp %v, res %v, tc %d", tc.expQuoTruncateMut.String(), tc.d1.String(), tcIndex)
+
+			// Receiver is not mutated
+			s.Require().Equal(tc.d1, copy, "exp %v, res %v, tc %d", tc.expQuoTruncateMut.String(), tc.d1.String(), tcIndex)
+
+			// Receiver is mutated.
+			tc.d1.QuoTruncateMut(tc.d2)
+
+			// Make sure d1 equals to expected
+			s.Require().True(tc.expQuoTruncateMut.Equal(tc.d1), "exp %v, res %v, tc %d", tc.expQuoTruncateMut.String(), tc.d1.String(), tcIndex)
+		}
+	}
+}
+

x/concentrated-liquidity/math/math.go

@@ -88,8 +88,7 @@ func CalcAmount0Delta(liq, sqrtPriceA, sqrtPriceB osmomath.BigDec, roundUp bool)
 	// Each intermediary step is truncated at precision end to get a smaller final amount.
 	// Note that the order of divisions is important here. First, we divide by a larger number (sqrtPriceB) and then by a smaller number (sqrtPriceA).
 	// This leads to a smaller error amplification.
-	// TODO (perf): QuoTruncate with no reallocation.
-	return liq.MulTruncate(diff).QuoTruncate(sqrtPriceB).QuoTruncate(sqrtPriceA)
+	return liq.MulTruncate(diff).QuoTruncateMut(sqrtPriceB).QuoTruncateMut(sqrtPriceA)
 }
 
 // CalcAmount1Delta takes the asset with the smaller liquidity in the pool as well as the sqrtpCur and the nextPrice and calculates the amount of asset 1