---
title: DFT
description: "计算任意长度实数序列、复数序列的正向/逆向傅里叶变换。"
url: https://www.hikunpeng.com/document/detail/zh/kunpengboostkithistory/240RC1/accel/kunpengaccel_hmpp_06_0160.html
sourcePath: /source/zh/kunpengboostkithistory/240RC1/accel/kunpengaccel_hmpp_06_0160.html
indexId: 8a8d7be2990fc133ed44a3e6a2a4e2b9723ebe5c183384ff3ef4fa395fbfd97977
---
# DFT

计算任意长度实数序列、复数序列的正向/逆向傅里叶变换。

正向变换：

逆向变换：


DFT（Discrete Fourier Transform）函数调用流程如下：

1. 调用Init初始化HmppsDFTPolicy结构体。
2. 调用CToC、RToC、CToR等主函数。
3. 最后调用Release释放。HmppsDFTPolicy函数所包含内存。

函数接口声明如下：

- 初始化操作：
  HmppResult HMPPS_DFTCToCInit_32f(int32_t len, int32_t direction, int32_t flag, HmppsDFTPolicy_32f **policy);

  HmppResult HMPPS_DFTCToCInit_64f(int32_t len, int32_t direction, int32_t flag, HmppsDFTPolicy_64f **policy);

  HmppResult HMPPS_DFTCToCInit_32fc(int32_t len, int32_t direction, int32_t flag, HmppsDFTPolicy_32fc **policy);

  HmppResult HMPPS_DFTCToCInit_64fc(int32_t len, int32_t direction, int32_t flag, HmppsDFTPolicy_64fc **policy);

  HmppResult HMPPS_DFTRToCInit_32f(int32_t len, int32_t flag, HmppsDFTPolicy_32f **policy);

  HmppResult HMPPS_DFTRToCInit_64f(int32_t len, int32_t flag, HmppsDFTPolicy_64f **policy);

  HmppResult HMPPS_DFTCToRInit_32f(int32_t len, int32_t flag, HmppsDFTPolicy_32f **policy);

  HmppResult HMPPS_DFTCToRInit_64f(int32_t len, int32_t flag, HmppsDFTPolicy_64f **policy);

- 主函数操作：
  HmppResult HMPPS_DFTCToC_32f(float *srcRe, float *srcIm, float *dstRe, float *dstIm, HmppsFFTPolicy_32f *policy);

  HmppResult HMPPS_DFTCToC_64f(double *srcRe, double *srcIm, double *dstRe, double *dstIm, HmppsFFTPolicy_64f *policy);

  HmppResult HMPPS_DFTCToC_32fc(Hmpp32fc *src, Hmpp32fc *dst, HmppsFFTPolicy_32fc *policy);

  HmppResult HMPPS_DFTCToC_64fc(Hmpp64fc *src, Hmpp64fc *dst, HmppsFFTPolicy_64fc *policy);

  HmppResult HMPPS_DFTRToC_32f(float *src, Hmpp32fc *dst, HmppsDFTPolicy_32f *policy);

  HmppResult HMPPS_DFTRToC_64f(double *src, Hmpp64fc *dst, HmppsDFTPolicy_64f *policy);

  HmppResult HMPPS_DFTCToR_32f(Hmpp32fc *src, float *dst, HmppsDFTPolicy_32f *policy);

  HmppResult HMPPS_DFTCToR_64f(Hmpp64fc *src, double *dst, HmppsDFTPolicy_64f *policy);

- 释放内存操作：
  HmppResult HMPPS_DFTCToCRelease_32f(HmppsDFTPolicy_32f *policy);

  HmppResult HMPPS_DFTCToCRelease_64f(HmppsDFTPolicy_64f *policy);

  HmppResult HMPPS_DFTCToCRelease_32fc(HmppsDFTPolicy_32fc *policy);

  HmppResult HMPPS_DFTCToCRelease_64fc(HmppsDFTPolicy_64fc *policy);

  HmppResult HMPPS_DFTRToCRelease_32f(HmppsDFTPolicy_32f *policy);

  HmppResult HMPPS_DFTRToCRelease_64f(HmppsDFTPolicy_64f *policy);

  HmppResult HMPPS_DFTCToRRelease_32f(HmppsDFTPolicy_32f *policy);

  HmppResult HMPPS_DFTCToRRelease_64f(HmppsDFTPolicy_64f *policy);


#### 参数

| 参数名 | 描述 | 取值范围 | 输入/输出 |
| --- | --- | --- | --- |
| len | FFT序列输入信号长度。 | (0, 227] | 输入 |
| direction | direction=1表示FFT正变换。 direction=\-1表示FFT逆变换。 用于CToC模式。 | ±1 | 输入 |
| flag | 结果正规化模式。 | HMPP\_FFT\_DIV\_FWD\_BY\_N、HMPP\_FFT\_DIV\_BWD\_BY\_N、HMPP\_FFT\_DIV\_BY\_SQRTN、HMPP\_FFT\_NODIV\_BY\_ANY | 输入 |
| policy（init函数中） | 双重指针，指向HmppsDFTPolicy结构体，结构体内包含DFT计算需要的一些信息和缓存块的首地址。 | 非空 | 输出 |
| policy（主函数和release函数） | 指针，指向HmppsDFTPolicy结构体。 | 非空 | 输入 |
| src | 指向源序列的指针。 | 非空 | 输入 |
| dst | 指向输出序列的指针。 | 非空 | 输出 |
| srcDst | 指向原址操作序列的指针。 | 非空 | 输入/输出 |


**表1 参数flag取值的说明**

| 取值 | 描述 |
| --- | --- |
| HMPP\_FFT\_DIV\_FWD\_BY\_N | 正向变换，1/N正规化模式。 |
| HMPP\_FFT\_DIV\_BWD\_BY\_N | 反向变换，1/N正规化模式。 |
| HMPP\_FFT\_DIV\_BY\_SQRTN | 正向或反向变换，1/N1/2正规化模式。 |
| HMPP\_FFT\_NODIV\_BY\_ANY | 正向或反向变换，不做特殊处理。 |


#### 返回值

- 成功：返回HMPP_STS_NO_ERR。
- 失败：返回错误码。


#### 错误码

| 错误码 | 描述 |
| --- | --- |
| HMPP\_STS\_NULL\_PTR\_ERR | 指针参数为空。 |
| HMPP\_STS\_SIZE\_ERR | len小于0。 |
| HMPP\_STS\_MALLOC\_FAILED | 所需的额外内存申请失败。 |
| HMPP\_STS\_FFT\_FLAG\_ERR | flag的值不在[1,4]范围内。 |


#### 注意

- 调用该接口计算DFT之前，必须调用HMPPS_DFTInit接口初始化HmppsDFTPolicy规范结构。
- HmppsDFTPolicy结构体初始化需在Init函数中进行申请的，用户无法自己进行该结构体申请定义。


#### 示例

- DFTCToC调用示例：

```
#define PI 3.14159265358979323846
void DFTCToC_Example()
{
Hmpp32fc src[8], dst[8];
for (int32_t i = 0; i < 8; i++) {
src[i].re = cos(2 * PI * i * 16 / 64);
src[i].im = 1;
}
HmppResult result;
HmppsDFTPolicy_32fc *policy = NULL;
result = HMPPS_DFTCToCInit_32fc(8, 1, HMPP_FFT_NODIV_BY_ANY, &policy);// 正向FFT
if (result != HMPP_STS_NO_ERR) {
printf("Create Policy Error!\n");
return;
}
result = HMPPS_DFTCToC_32fc(src, dst, policy);
if (result != HMPP_STS_NO_ERR) {
printf("DFT Error!\n");
return;
}
HMPPS_DFTCToCRelease_32fc(policy);
printf("dstRe =");
for (int32_t i = 0; i < 8; i++) {
printf("    %.2f", dst[i].re);
}
printf("\ndstIm =");
for (int32_t i = 0; i < 8; i++) {
printf("    %.2f", dst[i].im);
}
printf("\n");
}
```


  运行结果：

```
dstRe =    -0.00    -0.00    4.00    0.00    0.00    0.00    4.00    -0.00
dstIm =    8.00    -0.00    -0.00    -0.00    0.00    0.00    0.00    0.00
```


- DFTRToC/CToR调用示例：

```
void DFT_R_Example()
{
float src[8];
Hmpp32fc rtoc_dst[5];
float ctor_dst[8] = {0};
for (int32_t i = 0; i < 8; i++) {
src[i] = i + 1;
}
HmppResult result;
HmppsDFTPolicy_32f *policy = NULL;
result = HMPPS_DFTRToCInit_32f(8, HMPP_FFT_NODIV_BY_ANY, &policy);
if (result != HMPP_STS_NO_ERR) {
printf("DFTRToC Create Policy Error!\n");
return;
}
result = HMPPS_DFTRToC_32f(src, rtoc_dst, policy);
if (result != HMPP_STS_NO_ERR) {
printf("DFTRToC Error!\n");
return;
}
HMPPS_DFTRToCRelease_32f(policy);
printf("rtoc_dstRe =");
for (int32_t i = 0; i < 8; i++) {
printf("    %.2f", rtoc_dst[i].re);
}
printf("\nrtoc_dstIm =");
for (int32_t i = 0; i < 8; i++) {
printf("    %.2f", rtoc_dst[i].im);
}
printf("\n");
result = HMPPS_DFTCToRInit_32f(8, HMPP_FFT_NODIV_BY_ANY, &policy);
if (result != HMPP_STS_NO_ERR) {
printf("DFTCToR Create Policy Error!\n");
return;
}
result = HMPPS_DFTCToR_32f(rtoc_dst, ctor_dst, policy);
if (result != HMPP_STS_NO_ERR) {
printf("DFTCToR Error!\n");
return;
}
HMPPS_DFTCToRRelease_32f(policy);
printf("ctor_dst =");
for (int32_t i = 0; i < 8; i++) {
printf("    %.2f", ctor_dst[i]);
}
printf("\n");
}
```


  运行结果：

```
rtoc_dstRe =    36.00    -4.00    -4.00    -4.00    -4.00    1.00    3.00    5.00
rtoc_dstIm =    0.00    9.66    4.00    1.66    0.00    2.00    4.00    6.00
ctor_dst =    8.00    16.00    24.00    32.00    40.00    48.00    56.00    64.00
```