为什么在64位系统上float不是double？ [英] Why is float not a double on a 64-bit system?

问题描述

考虑到 int 在32位系统上为4个字节，在64位系统上为8个字节，为什么 float 没有处理相同？为什么64位系统上的 double ！= float 的大小？考虑到当我声明一个 int （这导致更高的性能），对于 float （这也会导致性能提高）不应该发生同样的情况吗？

Considering an int will be 4 bytes on a 32-bit system and 8 bytes on a 64-bit system, why is float not treated the same? Why is size of a double != size of a float on a 64-bit system? Considering that the best native integer type is selected when I declare an int (which results in higher performance), shouldn't the same happen for float (which also results in a performance increase)?

相关问题：声明一个类型 my_float （pardon的名称！）是一个坏主意，是 float 在32位系统上， double 在64位系统上？

Related question: Is it a bad idea to declare a type my_float (pardon the name!) that is float on 32-bit systems and double on 64-bit systems?

推荐答案

您的问题是基于一个错误的前提。在大多数现代64位系统上， int 仍然是4字节。为什么消耗两倍的内存和两倍的内存带宽，这么大的整数是如此罕见的需要？在典型的现代64位系统上，对64位整数的数学运算不如32位整数的数学运算，因此没有任何好处。

Your question is based on a false premise. On most modern 64-bit systems, int is still 4 bytes. Why consume twice as much memory and twice as much memory bandwidth when such large integers are so rarely needed? On typical modern 64-bit systems, math on 64-bit integers is not faster than math on 32-bit integers, so there's no benefit to be had.

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