stdxdecimal 0.5.0

Decimal Type for Phobos

This code is a work in progress for a new type Decimal that follows the "General Decimal Arithmetic Specification" http://speleotrove.com/decimal/decarith.html

Example

import stdxdecimal;

void main()
{
    auto d1 = decimal("1.23");
    auto d2 = decimal("1.23E-4");
    auto d3 = decimal("1.23E4");

    assert(d1.toString() == "1.23");
    assert(d2.toString() == "0.000123");
    assert(d3.toString() == "12300");

    auto d4 = d1 + d2;
    assert(d4.toString() == "1.230123");

    auto d5 = d3 - d1;
    assert(d5.toString() == "12298.87");

    auto d6 = decimal!(HighPrecision)("1.000000000000000000000000000000000000000000000000001");
    auto d7 = decimal!(HighPrecision)("1E-51");
    auto d8 = d6 + d7;
    assert(d8.toString() == "1.000000000000000000000000000000000000000000000000002");
}

Current Features

Feature	Implemented
Construction from strings/string-like ranges	✓
Construction from number types	✓
To decimal string	✓
To scientific string	❌
To engineering string	❌
All rounding types	❌
Overflow/Underflow Behavior	❌
Subnormal Behavior	❌
Clamping Behavior	❌
Equals	✓
toHash	❌
Compare	✓
Addition	✓
Subtraction	✓
Multiply	✓
Divide	✓
Divide-Integer	❌
Modulo	❌
DivMod	❌
opOpAssign +,-,*,/,^^	❌
Unary +,-,++,--	✓
opCast int,real,bool	❌
abs	✓
ln	❌
log10	❌
exp	❌
sqrt	❌
power	❌
reduce	❌

Current Performance

Run on a 15", 2015 Macbook Pro, (rounded to the nearest ms; test values purposely avoid rounding, which is the slowest part by far)

Test	BigInt	Decimal (P = 9)	Decimal (P = 19)	Decimal (P = 64)	Python Decimal	Python Decimal (64 Digits)
Addition (n = 5M)	594 ms	105 ms	152 ms	2,358 ms	799 ms	741 ms
Subtraction (n = 5M)	494 ms	103 ms	149 ms	2,247 ms	800 ms	830 ms
Multiplication (n = 5M)	156 ms	16 ms	1,689 ms	999 ms	695 ms	1541 ms
Division (n = 1M)	207 ms	25 ms	532 ms	11,116 ms	215 ms	416 ms
Sorting 1M Uniformly Random Numbers	592 ms	386 ms	502 ms	5,170 ms	1,536 ms	1,228 ms

Run It Yourself

D: ldc2 -O -release bench.d source/stdxdecimal/package.d && ./bench

Python:

import timeit

timeit.timeit("c = a + b", setup="from decimal import Decimal; a = Decimal(10000.12); b = Decimal(5000000); c = None", number=5000000)
timeit.timeit("c = a + b", setup="from decimal import Decimal; a = Decimal(1000000000000000000000000000000000000000000000000000000000000000); b = Decimal(5000000000000000000000000000000000000000000000000000000000000000); c = None", number=5000000)
timeit.timeit("c = a - b", setup="from decimal import Decimal; a = Decimal(10000.12); b = Decimal(5000000); c = None", number=5000000)
timeit.timeit("c = a - b", setup="from decimal import Decimal; a = Decimal('10000000000000000000000000000000000000000000000000000000000000.12'); b = Decimal('5000000000000000000000000000000000000000000000000000000000000000'); c = None", number=5000000)
timeit.timeit("c = a * b", setup="from decimal import Decimal; a = Decimal(10000.12); b = Decimal(5000000); c = None", number=5000000)
timeit.timeit("c = a * b", setup="from decimal import Decimal; a = Decimal('10000000000000000000000000000000000000000000000000000000000000.12'); b = Decimal('5000000000000000000000000000000000000000000000000000000000000000'); c = None", number=5000000)
timeit.timeit("c = a / b", setup="from decimal import Decimal; a = Decimal(10000.12); b = Decimal(5000000); c = None", number=1000000)
timeit.timeit("c = a / b", setup="from decimal import Decimal; a = Decimal('10000000000000000000000000000000000000000000000000000000000000.12'); b = Decimal('5000000000000000000000000000000000000000000000000000000000000000'); c = None", number=1000000)
timeit.timeit("c = sorted(a)", setup="from decimal import Decimal;import random; a = [Decimal(random.randint(-10000000, 10000000) * random.random()) for x in range(1000000)]", number=1)
timeit.timeit("c = sorted(a)", setup="from decimal import Decimal;import random; a = [Decimal(random.randint(-100000000000000000000000000000000000000000000000000, 100000000000000000000000000000000000000000000000000) * random.random()) for x in range(1000000)]", number=1)