---
title: clog2
description: "计算复数以2为底数的对数值。"
url: https://www.hikunpeng.com/document/detail/zh/kunpenghpcs/hpckit/devg/kunpengaccel_kml_0262.html
sourcePath: /source/zh/kunpenghpcs/hpckit/devg/kunpengaccel_kml_0262.html
indexId: 5aad87448e9fece1ab883539a03a84bd59152482416cdb7ffe521cbc19ea23a261
---
# clog2

计算复数以2为底数的对数值。

#### 接口定义

C interface：

float complex clog2f(float complex x);

double complex clog2(double complex x);


#### 参数

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| x | 在clog2f中，x是复数单精度浮点类型。 在clog2中，x是复数双精度浮点类型。 | 表示输入数据的浮点值。 | 输入 |


#### 返回值

- 返回x的以2为底的对数值结果y。
- 特殊值说明如下所示。| 输入值实部（x.real） | 输入值虚部（x.imag） | 输出值实部（y.real） | 输出值虚部（y.imag） |
| --- | --- | --- | --- |
| +0 | +0 | \-inf | +0 |
| +0 | \-0 | \-inf | \-0 |
| +0 | inf | inf | 0x40022123045b5dec(pi/2ln2) |
| +0 | \-inf | inf | 0xc0022123045b5dec(\-pi/2ln2) |
| +0 | snan | nan | nan |
| +0 | \-snan | nan | nan |
| +0 | qnan | nan | nan |
| +0 | \-qnan | nan | nan |
| \-0 | +0 | \-inf | 0x40122123045b5dec(pi/ln2) |
| \-0 | \-0 | \-inf | 0xc0122123045b5dec(\-pi/ln2) |
| \-0 | inf | inf | 0x40022123045b5dec(pi/2ln2) |
| \-0 | \-inf | inf | 0xc0022123045b5dec(\-pi/2ln2) |
| \-0 | snan | nan | nan |
| \-0 | \-snan | nan | nan |
| \-0 | qnan | nan | nan |
| \-0 | \-qnan | nan | nan |
| inf | +0 | inf | +0 |
| inf | \-0 | inf | \-0 |
| inf | inf | inf | 0x3ff22123045b5dec(pi/4ln2) |
| inf | \-inf | inf | 0xbff22123045b5dec(\-pi/4ln2) |
| inf | snan | inf | nan |
| inf | \-snan | inf | nan |
| inf | qnan | inf | nan |
| inf | \-qnan | inf | nan |
| \-inf | +0 | inf | 0x40122123045b5dec(pi/ln2) |
| \-inf | \-0 | inf | 0xc0122123045b5dec(\-pi/ln2) |
| \-inf | inf | inf | 0x400b31b486890ce1(3\*pi/4ln2) |
| \-inf | \-inf | inf | 0xc00b31b486890ce1(\-3\*pi/4ln2) |
| \-inf | snan | inf | nan |
| \-inf | \-snan | inf | nan |
| \-inf | qnan | inf | nan |
| \-inf | \-qnan | inf | nan |
| snan | +0 | nan | nan |
| snan | \-0 | nan | nan |
| snan | inf | inf | nan |
| snan | \-inf | inf | nan |
| snan | snan | nan | nan |
| snan | \-snan | nan | nan |
| snan | qnan | nan | nan |
| snan | \-qnan | nan | nan |
| \-snan | +0 | nan | nan |
| \-snan | \-0 | nan | nan |
| \-snan | inf | inf | nan |
| \-snan | \-inf | inf | nan |
| \-snan | snan | nan | nan |
| \-snan | \-snan | nan | nan |
| \-snan | qnan | nan | nan |
| \-snan | \-qnan | nan | nan |
| qnan | +0 | nan | nan |
| qnan | \-0 | nan | nan |
| qnan | inf | inf | nan |
| qnan | \-inf | inf | nan |
| qnan | snan | nan | nan |
| qnan | \-snan | nan | nan |
| qnan | qnan | nan | nan |
| qnan | \-qnan | nan | nan |
| \-qnan | +0 | nan | nan |
| \-qnan | \-0 | nan | nan |
| \-qnan | inf | inf | nan |
| \-qnan | \-inf | inf | nan |
| \-qnan | snan | nan | nan |
| \-qnan | \-snan | nan | nan |
| \-qnan | qnan | nan | nan |
| \-qnan | \-qnan | nan | nan |


#### 依赖

C: "kc.h"


#### 示例

C interface：```
// typical usage
    double x1 = INFINITY, y1 = INFINITY;
    double x2 = 2.0, y2 = 3.0;
    double x3 = -2.5, y3 = -3.4;
    double x4 = NAN, y4 = NAN;
    double x5 = 0, y5 = 0;
    double complex z1 = clog2(__builtin_complex(x1, y1));
    double complex z2 = clog2(__builtin_complex(x2, y2));
    double complex z3 = clog2(__builtin_complex(x3, y3));
    double complex z4 = clog2(__builtin_complex(x4, y4));
    double complex z5 = clog2(__builtin_complex(x5, y5));
    // print result
    printf("/*\n");
    printf(" * clog2(%.2f + %.2f*I) = %.6f + %.6f*I\n", x1, y1, __real__(z1), __imag__(z1));
    printf(" * clog2(%.2f + %.2f*I) = %.6f + %.6f*I\n", x2, y2, __real__(z2), __imag__(z2));
    printf(" * clog2(%.2f + %.2f*I) = %.6f + %.6f*I\n", x3, y3, __real__(z3), __imag__(z3));
    printf(" * clog2(%.2f + %.2f*I) = %.6f + %.6f*I\n", x4, y4, __real__(z4), __imag__(z4));
    printf(" * clog2(%.2f + %.2f*I) = %.6f + %.6f*I\n", x5, y5, __real__(z5), __imag__(z5));
    printf(" **/\n");
   /*
    * clog2(inf + inf*I) = inf + 1.133090*I
    * clog2(2.00 + 3.00*I) = 1.850220 + 1.417872*I
    * clog2(-2.50 + -3.40*I) = 2.077308 + -3.180882*I
    * clog2(nan + nan*I) = nan + nan*I
    * clog2(0.00 + 0.00*I) = -inf + 0.000000*I
    **/
```