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5 commits

Author SHA1 Message Date
Philip Dubé
ceada80758
Merge d538aec685 into 547861c49b 2024-04-03 21:15:58 +00:00
Philip Dubé
d538aec685 remove copy, don't need Abs(d.value)
9007199254740992 converts to float64
2024-04-03 21:15:48 +00:00
Philip Dubé
0a79029c95 feedback, fixes bug 2024-04-03 21:15:48 +00:00
Philip Dubé
afe2a66041 Optimize NumDigits
Dividing BitLen by math.Log2(10) is what math/big does underneath

Not including the Int64/Uint64 check makes this slightly slower than old method

Included 2 benchmarks, for 10 digit numbers & 100 digit numbers:

-- before
> go test -bench=NumDigit -run=NumDigit
goos: linux
goarch: amd64
pkg: github.com/shopspring/decimal
cpu: AMD Ryzen 7 7840U w/ Radeon  780M Graphics
BenchmarkDecimal_NumDigits10-16     	18317293	        63.87 ns/op
BenchmarkDecimal_NumDigits100-16    	 3645015	       329.6 ns/op

-- after
...
BenchmarkDecimal_NumDigits10-16     	143781325	         8.488 ns/op
BenchmarkDecimal_NumDigits100-16    	 5931247	       207.4 ns/op
2024-04-03 21:15:48 +00:00
Philip Dubé
547861c49b
Avoid reallocation of initial slice in MarshalBinary (GobEncode) (#355) 2024-04-03 22:12:19 +02:00
2 changed files with 65 additions and 20 deletions

View file

@ -1224,14 +1224,32 @@ func (d Decimal) Ln(precision int32) (Decimal, error) {
}
// NumDigits returns the number of digits of the decimal coefficient (d.Value)
// Note: Current implementation is extremely slow for large decimals and/or decimals with large fractional part
func (d Decimal) NumDigits() int {
d.ensureInitialized()
// Note(mwoss): It can be optimized, unnecessary cast of big.Int to string
if d.IsNegative() {
return len(d.value.String()) - 1
if d.value == nil {
return 1
}
return len(d.value.String())
if d.value.IsInt64() {
i64 := d.value.Int64()
if i64 <= (1<<53) && i64 >= -(1<<53) {
if i64 == 0 {
return 1
}
return int(math.Log10(math.Abs(float64(i64)))) + 1
}
}
estimatedNumDigits := int(float64(d.value.BitLen()) / math.Log2(10))
// estimatedNumDigits (lg10) may be off by 1, need to verify
digitsBigInt := big.NewInt(int64(estimatedNumDigits))
errorCorrectionUnit := digitsBigInt.Exp(tenInt, digitsBigInt, nil)
if d.value.CmpAbs(errorCorrectionUnit) >= 0 {
return estimatedNumDigits + 1
}
return estimatedNumDigits
}
// IsInteger returns true when decimal can be represented as an integer value, otherwise, it returns false.
@ -1784,19 +1802,18 @@ func (d *Decimal) UnmarshalBinary(data []byte) error {
// MarshalBinary implements the encoding.BinaryMarshaler interface.
func (d Decimal) MarshalBinary() (data []byte, err error) {
// Write the exponent first since it's a fixed size
v1 := make([]byte, 4)
binary.BigEndian.PutUint32(v1, uint32(d.exp))
// Add the value
var v2 []byte
if v2, err = d.value.GobEncode(); err != nil {
return
// exp is written first, but encode value first to know output size
var valueData []byte
if valueData, err = d.value.GobEncode(); err != nil {
return nil, err
}
// Write the exponent in front, since it's a fixed size
expData := make([]byte, 4, len(valueData)+4)
binary.BigEndian.PutUint32(expData, uint32(d.exp))
// Return the byte array
data = append(v1, v2...)
return
return append(expData, valueData...), nil
}
// Scan implements the sql.Scanner interface for database deserialization.

View file

@ -121,6 +121,34 @@ func BenchmarkDecimal_RoundCash_Five(b *testing.B) {
}
}
func numDigits(b *testing.B, want int, val Decimal) {
b.Helper()
for i := 0; i < b.N; i++ {
if have := val.NumDigits(); have != want {
b.Fatalf("\nHave: %q\nWant: %q", have, want)
}
}
}
func BenchmarkDecimal_NumDigits10(b *testing.B) {
numDigits(b, 10, New(3478512345, -3))
}
func BenchmarkDecimal_NumDigits100(b *testing.B) {
s := make([]byte, 102)
for i := range s {
s[i] = byte('0' + i%10)
}
s[0] = '-'
s[100] = '.'
d, err := NewFromString(string(s))
if err != nil {
b.Log(d)
b.Error(err)
}
numDigits(b, 100, d)
}
func Benchmark_Cmp(b *testing.B) {
decimals := DecimalSlice([]Decimal{})
for i := 0; i < 1000000; i++ {
@ -132,7 +160,7 @@ func Benchmark_Cmp(b *testing.B) {
}
}
func Benchmark_decimal_Decimal_Add_different_precision(b *testing.B) {
func BenchmarkDecimal_Add_different_precision(b *testing.B) {
d1 := NewFromFloat(1000.123)
d2 := NewFromFloat(500).Mul(NewFromFloat(0.12))
@ -143,7 +171,7 @@ func Benchmark_decimal_Decimal_Add_different_precision(b *testing.B) {
}
}
func Benchmark_decimal_Decimal_Sub_different_precision(b *testing.B) {
func BenchmarkDecimal_Sub_different_precision(b *testing.B) {
d1 := NewFromFloat(1000.123)
d2 := NewFromFloat(500).Mul(NewFromFloat(0.12))
@ -154,7 +182,7 @@ func Benchmark_decimal_Decimal_Sub_different_precision(b *testing.B) {
}
}
func Benchmark_decimal_Decimal_Add_same_precision(b *testing.B) {
func BenchmarkDecimal_Add_same_precision(b *testing.B) {
d1 := NewFromFloat(1000.123)
d2 := NewFromFloat(500.123)
@ -165,7 +193,7 @@ func Benchmark_decimal_Decimal_Add_same_precision(b *testing.B) {
}
}
func Benchmark_decimal_Decimal_Sub_same_precision(b *testing.B) {
func BenchmarkDecimal_Sub_same_precision(b *testing.B) {
d1 := NewFromFloat(1000.123)
d2 := NewFromFloat(500.123)