有效地将两个整数x和y转换为浮点数x.y [英] Efficiently convert two Integers x and y into the float x.y

问题描述

给出两个整数X和Y，在C ++中将它们转换为X.Y浮点值的最有效方法是什么?

Given two integers X and Y, whats the most efficient way of converting them into X.Y float value in C++?

例如

 X = 3, Y = 1415 -> 3.1415

 X = 2, Y = 12   -> 2.12

推荐答案

以下是我的机器上一些鸡尾酒餐巾基准测试结果，这些结果截止到将两个int转换为float的所有解决方案写作.

Here are some cocktail-napkin benchmark results, on my machine, for all solutions converting two ints to a float, as of the time of writing.

注意:我现在添加了自己的解决方案，该方法似乎效果很好，因此存在偏见！请仔细检查我的结果.

Caveat: I've now added a solution of my own, which seems to do well, and am therefore biased! Please double-check my results.

Test                              Iterations    ns / iteration
--------------------------------------------------------------
@aliberro's conversion v2         79,113,375                13
@3Dave's conversion               84,091,005                12
@einpoklum's conversion        1,966,008,981                 0
@Ripi2's conversion               47,374,058                21
@TarekDakhran's conversion     1,960,763,847                 0

• CPU:四核Intel Core i5-7600K速度/最小/最大:4000/800/4200 MHz
• Devuan GNU/Linux 3
• 内核:5.2.0-3-amd64 x86_64
• GCC 9.2.1，带有标志:-O3 -march=native -mtune=native
• CPU: Quad Core Intel Core i5-7600K speed/min/max: 4000/800/4200 MHz
• Devuan GNU/Linux 3
• Kernel: 5.2.0-3-amd64 x86_64
• GCC 9.2.1, with flags: -O3 -march=native -mtune=native

基准代码(Github Gist).

Benchmark code (Github Gist).

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