Java Math.pow的错误结果 [英] Wrong result by Java Math.pow

问题描述

如果您尝试运行以下代码

If you try to run the following code

public class Main {
   public static void main(String[] args) {
       long a = (long)Math.pow(13, 15);
       System.out.println(a + " " + a%13);
   }
}

您将获得51185893014090752 8

You will get "51185893014090752 8"

13 ^ 15 的正确值为 51185893014090757 ，即大于 Math返回的结果。 pow 5 。可能导致它的任何想法？

The correct value of 13^15 is 51185893014090757, i.e. greater than the result returned by Math.pow by 5. Any ideas of what may cause it?

推荐答案

你已经超过了有效位数（~15到16）双精度浮点值。一旦你这样做，你就不能指望你的结果中最不重要的数字真正有意义/精确。

You've exceeded the number of significant digits available (~15 to 16) in double-precision floating-point values. Once you do that, you can't expect the least significant digit(s) of your result to actually be meaningful/precise.

如果你需要在Java中任意精确的算术，考虑使用 BigInteger 和 BigDecimal 。

If you need arbitrarily precise arithmetic in Java, consider using BigInteger and BigDecimal.

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