性能报告显示“__libm_pow_l9" [英] perf report showing "__libm_pow_l9"

问题描述

我正在使用 perf 来分析我的程序，这涉及大量使用 exp() 和 pow().代码编译使用

I am using perf to profile my program, which involves loads of use of exp() and pow(). The code was compiled use

icc  -g -fno-omit-frame-pointer test.c

并通过以下方式进行分析:

and profiled with:

perf record -g ./a.out

后面跟着:

perf report -g 'graph,0.5,caller'

和 perf 给出:

__libm_exp_l9() 和 __libm_pow_l9() 两个函数消耗了大量的计算能力.

the two functions __libm_exp_l9() and __libm_pow_l9() are consuming considerable amount of computational power.

所以我想知道它们是否分别是 exp() 和 pow() 的别名?或者有什么建议可以阅读这里的报告?谢谢.

So I am wondering if they are just alias to exp() and pow(), respectively? Or any suggestions to read in the report here? Thanks.

推荐答案

它们不是别名，而是函数的内部实现.数学库通常具有多个版本的函数，具体取决于使用的处理器、指令集或参数.

They are not aliases, but internal implementation of the functions. Mathematical libraries have usually several versions of the functions depending on used processor, instruction set, or arguments.

没有什么可担心的.Exp 和 Pow 是比指令(通常)更复杂的函数，因此它们需要一些时间.不幸的是，我没有找到对它们的任何引用(英特尔数学库可能不是开源的)，但这是对函数使用内部命名空间名称的常见做法.

There is nothing to worry about. Exp and Pow are functions that are more complex than just an instructions (usually) and therefore they take some time. Unfortunately I didn't find any reference to them (Intel mathematical library is probably not opensource), but this is common practice to use internal, namespaced names for function.

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