更快的替代Convert.ToDouble(string) [英] Faster alternative to Convert.ToDouble(string)

问题描述

是否有比 Convert.ToDouble 更快的更快方式将 string 转换为 double ?

Is there a faster way to convert a string to double than Convert.ToDouble?

我监视了 System.Convert.ToDouble(string)调用及其对我的应用程序性能的降低.

I have monitored System.Convert.ToDouble(string) calls and its degrading my app performance.

Convert.ToDouble("1.34515");

杰弗里·萨克斯(Jeffrey Sax)的工作答案:

static decimal[] decimalPowersOf10 = { 1m, 10m, 100m, 1000m, 10000m, 100000m, 1000000m }; 
static decimal CustomParseDecimal(string input) { 
    long n = 0; 
    int decimalPosition = input.Length; 
    for (int k = 0; k < input.Length; k++) { 
        char c = input[k]; 
        if (c == '.') 
            decimalPosition = k + 1; 
        else 
            n = (n * 10) + (int)(c - '0'); 
    } 
    return n / decimalPowersOf10[input.Length - decimalPosition]; 

}

之后

推荐答案

通过使用 NumberStyles 和 IFormatProvider (即 CultureInfo ):

var style = System.Globalization.NumberStyles.AllowDecimalPoint;
var culture = System.Globalization.CultureInfo.InvariantCulture;
double.TryParse("1.34515", style, culture, out x);

Convert.ToDouble 和 Double.Parse 或 Double.TryParse 都必须假定输入可以是任何格式.如果您确定输入内容具有特定格式，则可以编写自定义解析器，以实现更好的性能.

Both Convert.ToDouble and Double.Parse or Double.TryParse have to assume the input can be in any format. If you know for certain that your input has a specific format, you can write a custom parser that performs much better.

这里是转换为十进制的代码.转换为 double 的过程与此类似.

Here's one that converts to decimal. Conversion to double is similar.

static decimal CustomParseDecimal(string input) {
    long n = 0;
    int decimalPosition = input.Length;
    for (int k = 0; k < input.Length; k++) {
        char c = input[k];
        if (c == '.')
            decimalPosition = k + 1;
        else
            n = (n * 10) + (int)(c - '0');
    }
    return new decimal((int)n, (int)(n >> 32), 0, false, (byte)(input.Length - decimalPosition));
}

我的基准测试表明，对于 decimal ，此速度比原始速度快大约5倍，如果使用int，则最多可以快12倍.

My benchmarks show this to be about 5 times faster than the original for decimal, and up to 12 times if you use ints.

这篇关于更快的替代Convert.ToDouble(string)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！