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decimal: implement Log method
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@eapenkin
eapenkin authored Oct 19, 2024
1 parent d5ed3ca commit de7a393
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20 changes: 16 additions & 4 deletions .github/workflows/go.yml
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Expand Up @@ -81,7 +81,10 @@ jobs:
run: go test -fuzztime 60s -fuzz ^FuzzDecimal_AddMul$

- name: Run fuzzing for fused multiply-addition
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Add_Mul_AddMul$
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Add_AddMul$

- name: Run fuzzing for fused multiply-addition
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Mul_AddMul$

- name: Run fuzzing for division
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Quo$
Expand All @@ -90,22 +93,31 @@ jobs:
run: go test -fuzztime 60s -fuzz ^FuzzDecimal_AddQuo$

- name: Run fuzzing for fused quotient-addition
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Add_Quo_AddQuo$
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Add_AddQuo$

- name: Run fuzzing for fused quotient-addition
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Quo_AddQuo$

- name: Run fuzzing for integer division and remainder
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_QuoRem$

- name: Run fuzzing for square root
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Sqrt_Pow$
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Sqrt_PowInt$

- name: Run fuzzing for exponential and logarithm
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Log_Exp$

- name: Run fuzzing for comparison
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Cmp$

- name: Run fuzzing for comparison and subtraction
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Cmp_Sub$
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Sub_Cmp$

- name: Run fuzzing for constructor
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_New$

- name: Run fuzzing for trimming
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Trim$

- name: Run fuzzing for padding
run: go test -fuzztime 20s -fuzz ^FuzzDecimal_Pad$
10 changes: 8 additions & 2 deletions CHANGELOG.md
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@@ -1,5 +1,11 @@
# Changelog

## [0.1.32] - 2024-09-28

- Implemented `Decimal.Log`.
- `Decimal.PowInt` always correctly rounds the result.
- Deprecated `Decimal.Pow`.

## [0.1.31] - 2024-08-30

### Added
Expand Down Expand Up @@ -126,7 +132,7 @@

### Changed

- Improved accuracy of `Decimal.Pow` for negative powers.
- Improved accuracy of `Decimal.PowInt` for negative powers.
- Reviewed and improved documentation.

## [0.1.11] - 2023-09-21
Expand Down Expand Up @@ -160,7 +166,7 @@

### Changed

- Improved accuracy of `Decimal.Pow`.
- Improved accuracy of `Decimal.PowInt`.

## [0.1.7] - 2023-08-20

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83 changes: 44 additions & 39 deletions README.md
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Expand Up @@ -18,14 +18,16 @@ This package is designed specifically for use in transactional financial systems
- **Banker's Rounding** - Uses [half-to-even] rounding, also known as
"banker's rounding", to minimize cumulative rounding errors commonly seen
in financial calculations.
- **Accurate Artihmetic** - All methods are precisely rounded to a 19-digit
precision, ensuring results are as close as possible to the true mathematical value.
- **No Panics** - All methods are panic-free, returning errors instead of crashing
your application in cases such as overflow or division by zero.
- **Zero Heap Allocation** - Optimized to avoid heap allocations,
- **No Heap Allocations** - Optimized to avoid heap allocations,
reducing garbage collector impact during arithmetic operations.
- **Simple String Representation** - Decimals are represented in a strightforward
format avoiding the complexities of scientific or engineering notations.
- **Correctness** - Arithmetic operations are cross-validated against the
[cockroachdb/apd] and [shopspring/decimal] packages throught extensive [fuzz testing].
- **Rigorous Testing** - All methods are cross-validated against
the [cockroachdb/apd] and [shopspring/decimal] packages throught extensive [fuzz testing].

## Getting Started

Expand Down Expand Up @@ -57,39 +59,41 @@ func main() {
f, _ := decimal.NewFromFloat64(2.567) // f = 2.567
g, _ := decimal.NewFromInt64(7, 896, 3) // g = 7.896

// Operations
fmt.Println(d.Add(e)) // 8 + 12.5
fmt.Println(d.Sub(e)) // 8 - 12.5
fmt.Println(d.SubAbs(e)) // abs(8 - 12.5)
// Arithmetic operations
fmt.Println(d.Add(e)) // 8 + 12.5
fmt.Println(d.Sub(e)) // 8 - 12.5
fmt.Println(d.SubAbs(e)) // abs(8 - 12.5)

fmt.Println(d.Mul(e)) // 8 * 12.5
fmt.Println(d.AddMul(e, f)) // 8 + 12.5 * 2.567
fmt.Println(d.SubMul(e, f)) // 8 - 12.5 * 2.567
fmt.Println(d.Mul(e)) // 8 * 12.5
fmt.Println(d.AddMul(e, f)) // 8 + 12.5 * 2.567
fmt.Println(d.SubMul(e, f)) // 8 - 12.5 * 2.567
fmt.Println(d.PowInt(2)) // 8²

fmt.Println(d.Quo(e)) // 8 / 12.5
fmt.Println(d.AddQuo(e, f)) // 8 + 12.5 / 2.567
fmt.Println(d.SubQuo(e, f)) // 8 - 12.5 / 2.567
fmt.Println(d.QuoRem(e)) // 8 div 12.5, 8 mod 12.5
fmt.Println(d.Inv()) // 1 / 8
fmt.Println(d.Quo(e)) // 8 / 12.5
fmt.Println(d.AddQuo(e, f)) // 8 + 12.5 / 2.567
fmt.Println(d.SubQuo(e, f)) // 8 - 12.5 / 2.567
fmt.Println(d.QuoRem(e)) // 8 div 12.5, 8 mod 12.5
fmt.Println(d.Inv()) // 1 / 8

fmt.Println(d.Sqrt()) // √8
fmt.Println(d.Exp()) // exp(8)
fmt.Println(d.Pow(2)) // 8²
// Transcendental functions
fmt.Println(d.Sqrt()) // √8
fmt.Println(d.Exp()) // exp(8)
fmt.Println(d.Log()) // ln(8)

// Rounding to 2 decimal places
fmt.Println(g.Round(2)) // 7.90
fmt.Println(g.Ceil(2)) // 7.90
fmt.Println(g.Floor(2)) // 7.89
fmt.Println(g.Trunc(2)) // 7.89
fmt.Println(g.Round(2)) // 7.90
fmt.Println(g.Ceil(2)) // 7.90
fmt.Println(g.Floor(2)) // 7.89
fmt.Println(g.Trunc(2)) // 7.89

// Conversions
fmt.Println(f.Int64(9)) // 2 567000000
fmt.Println(f.Float64()) // 2.567
fmt.Println(f.String()) // 2.567
fmt.Println(f.Int64(9)) // 2 567000000
fmt.Println(f.Float64()) // 2.567
fmt.Println(f.String()) // 2.567

// Formatting
fmt.Printf("%.2f", f) // 2.57
fmt.Printf("%.2k", f) // 256.70%
fmt.Printf("%.2f", f) // 2.57
fmt.Printf("%.2k", f) // 256.70%
}
```

Expand All @@ -104,15 +108,15 @@ For examples related to financial calculations, see the `money` package

Comparison with other popular packages:

| Feature | govalues | [cockroachdb/apd] v3.2.1 | [shopspring/decimal] v1.4.0 |
| ---------------- | ------------ | ------------------------ | --------------------------- |
| Speed | High | Medium | Low[^reason] |
| Mutability | Immutable | Mutable[^reason] | Immutable |
| Memory Footprint | Low | Medium | High |
| Panic Free | Yes | Yes | No[^divzero] |
| Precision | 19 digits | Arbitrary | Arbitrary |
| Default Rounding | Half to even | Half up | Half away from 0 |
| Context | Implicit | Explicit | Implicit |
| Feature | govalues | [cockroachdb/apd] v3.2.1 | [shopspring/decimal] v1.4.0 |
| ----------------- | --------- | ------------------------ | --------------------------- |
| Speed | High | Medium | Low[^reason] |
| Mutability | Immutable | Mutable[^reason] | Immutable |
| Heap Allocations | No | Medium | High |
| Panic Free | Yes | Yes | No[^divzero] |
| Precision | 19 digits | Arbitrary | Arbitrary |
| Correctly Rounded | Yes | No | No |
| Context | Implicit | Explicit | Implicit |

[^reason]: decimal package was created simply because [shopspring/decimal] was
too slow and [cockroachdb/apd] was mutable.
Expand All @@ -134,11 +138,12 @@ cpu: AMD Ryzen 7 3700C with Radeon Vega Mobile Gfx
| Mul | 2 * 3 | 16.93n | 62.20n | 146.00n | +267.40% | +762.37% |
| Quo | 2 / 4 (exact) | 59.52n | 176.95n | 657.40n | +197.30% | +1004.50% |
| Quo | 2 / 3 (inexact) | 391.60n | 976.80n | 2962.50n | +149.39% | +656.42% |
| Pow | 1.1^60 | 950.90n | 3302.50n | 4599.50n | +247.32% | +383.73% |
| Pow | 1.01^600 | 3.45µ | 10.67µ | 18.67µ | +209.04% | +440.89% |
| Pow | 1.001^6000 | 5.94µ | 20.50µ | 722.22µ | +244.88% | +12052.44% |
| PowInt | 1.1^60 | 950.90n | 3302.50n | 4599.50n | +247.32% | +383.73% |
| PowInt | 1.01^600 | 3.45µ | 10.67µ | 18.67µ | +209.04% | +440.89% |
| PowInt | 1.001^6000 | 5.94µ | 20.50µ | 722.22µ | +244.88% | +12052.44% |
| Sqrt | √2 | 3.40µ | 4.96µ | 2101.86µ | +46.00% | +61755.71% |
| Exp | exp(0.5) | 8.35µ | 39.28µ | 20.06µ | +370.58% | +140.32% |
| Log | ln(0.5) | 54.89µ | 129.01µ | 151.55µ | +135.03% | +176.10% |
| Parse | 1 | 16.52n | 76.30n | 136.55n | +362.00% | +726.82% |
| Parse | 123.456 | 47.37n | 176.90n | 242.60n | +273.44% | +412.14% |
| Parse | 123456789.1234567890 | 85.49n | 224.15n | 497.95n | +162.19% | +482.47% |
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