---
title: sqrt
description: "计算x的平方根。"
url: https://www.hikunpeng.com/document/detail/zh/kunpengboostkithistory/2200/accel/kunpengaccel_kml_16_0202.html
sourcePath: /source/zh/kunpengboostkithistory/2200/accel/kunpengaccel_kml_16_0202.html
indexId: 62f57d1c8e5169634d419d28504301a9a92b41673d3185eebe5d837eeacf0f4074
---
# sqrt

计算x的平方根。

#### 接口定义

C interface：

float sqrtf(float x);

double sqrt(double x);

Fortran interface：

RES = SQRTF(X);

RES = SQRT(X);


#### 参数

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| x | 在sqrtf中，x是单精度浮点类型。 在sqrt中，x是双精度浮点类型。 | 表示输入数据的浮点值。 | 输入 |


#### 返回值

- 输入x为±0，返回±0。
- 输入x为+∞，返回+∞。
- 输入x为nan，返回nan。


#### 依赖

C: "km.h"

Fortran: "km.f03"


#### 示例

C interface：

```
// typical usage
double x1 = 1.0, x2 = 2.0, x3 = 3.0, x4 = 4.0;
// special handing
double a = 0.0, b = INFINITY, c = -INFINITY, d = NAN;
// print result
printf("sqrt(1.0) = %.15f\n", sqrt(x1));
printf("sqrt(2.0) = %.15f\n", sqrt(x2));
printf("sqrt(3.0) = %.15f\n", sqrt(x3));
printf("sqrt(4.0) = %.15f\n", sqrt(x4));
printf("sqrt(0.0) = %.15f\n", sqrt(a));
printf("sqrt(INFINITY) = %.15f\n", sqrt(b));
printf("sqrt(-INFINITY) = %.15f\n", sqrt(c));
printf("sqrt(NAN) = %.15f\n", sqrt(d));
/*
*  sqrt(1.0) = 1.000000000000000
*  sqrt(2.0) = 1.414213562373095
*  sqrt(3.0) = 1.732050807568877
*  sqrt(4.0) = 2.000000000000000
*  sqrt(0.0) = 0.000000000000000
*  sqrt(INFINITY) = inf
*  sqrt(-INFINITY) = -inf
*  sqrt(NAN) = nan
* */
```

Fortran interface：

```
REAL(8) :: X = 3.0
PRINT*,  SQRT(X)
!
! OUTPUT
!     1.732050807568877
!
```