---
title: kml_fft(f)_plan_dft_r2c
description: "建立单个连续数据序列n维R2C变换的plan。"
url: https://www.hikunpeng.com/document/detail/zh/kunpengboostkithistory/2200/accel/kunpengaccel_kml_16_0136.html
sourcePath: /source/zh/kunpengboostkithistory/2200/accel/kunpengaccel_kml_16_0136.html
indexId: fd9c4c946f346d1c42d770aae6b567b31ff08782b7197df70d564be149eaed1474
---
# kml_fft(f)_plan_dft_r2c

建立单个连续数据序列n维R2C变换的plan。

#### 接口定义

C interface：

kml_fft_plan kml_fft_plan_dft_r2c(int rank, const int *n, double *in, kml_fft_complex *out, unsigned flags);

kml_fftf_plan kml_fftf_plan_dft_r2c(int rank, const int *n, float *in, kml_fftf_complex *out, unsigned flags);

Fortran interface：

RES = KML_FFT_PLAN_DFT_R2C(RANK, N, IN, OUT, FLAGS);

RES = KML_FFTF_PLAN_DFT_R2C(RANK, N, IN, OUT, FLAGS);


#### 返回值

函数返回一个kml_fft(f)_plan类型的结构体指针。将该对象作为参数传入kml_fft(f)_execute函数中使用，将对当前提供的输入in和输出out执行FFT变换；另外，也可以通过将该对象作为参数传入kml_fft(f)_execute_dft_r2c函数中以对新的输入in和输出out执行FFT变换。

如果函数返回非空指针，则表示plan执行成功，否则表示执行失败。


#### 参数

| 参数名 | 数据类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| rank | int | FFT变换的维度是rank，约束：1 <= rank <= 3。 | 输入 |
| n | const int\* | n是维度为rank的数组，包含FFT序列每一维度的大小，约束：n[i] >= 1, for i in 0 to rank \- 1。 | 输入 |
| in | 双精度：double\* 单精度：float\* | 输入待变换的数据。 | 输入 |
| out | 双精度：kml\_fft\_complex\* 单精度：kml\_fftf\_complex\* | 输出快速傅里叶变换后的数据。 | 输出 |
| flags | unsigned int | planning选项，未使用。 | 输入 |


#### 依赖

C: "kfft.h"

Fortran: "kfft.f03"


#### 示例

C interface：

```
int rank = 2;
int *n;
n = (int*)kml_fft_malloc(sizeof(int) * rank);
n[0] = 2;
n[1] = 4;
double init[8] = {1, 2, 3, 4, 5, 6, 7, 8};
double *in;
in = (double*)kml_fft_malloc(sizeof(double) * n[0] * n[1]);
for (int i = 0; i < n[0] * n[1]; i++) {
in[i] = init[i];
}
kml_fft_complex *out;
out = (kml_fft_complex*)kml_fft_malloc(sizeof(kml_fft_complex) * n[0] * (n[1] / 2 + 1));
kml_fft_plan plan;
plan = kml_fft_plan_dft_r2c(rank, n, in, out, KML_FFT_ESTIMATE);
kml_fft_execute_dft_r2c(plan, in, out);
kml_fft_destroy_plan(plan);
kml_fft_free(n);
kml_fft_free(in);
kml_fft_free(out);
/*
* out = {{3.600000e+01, 0.000000e+00}, {-4.000000e+00, 4.000000e+00},
*        {-4.000000e+00, 0.000000e+00}, {-1.600000e+01, 0.000000e+00},
*        {0.000000e+00, 0.000000e+00}, {0.000000e+00, 0.000000e+00}}
*/
```

Fortran interface：

```
INTEGER(C_INT) :: RANK = 2
INTEGER(C_INT) :: N(2)
REAL(C_DOUBLE) :: INIT(8)
REAL(C_DOUBLE), POINTER :: IN
TYPE(KML_FFT_COMPLEX), POINTER :: OUT
TYPE(C_PTR) :: PIN, POUT
INTEGER(C_SIZE_T) :: RSIZE, CSIZE
RSIZE = N(1) * N(2)
CSIZE = N(1) * (N(2) / 2 + 1)
PIN = KML_FFT_MALLOC(8 * RSIZE)
POUT = KML_FFT_MALLOC(16 * CSIZE)
CALL C_F_POINTER(PIN, IN, SHAPE=[RSIZE])
CALL C_F_POINTER(POUT, OUT, SHAPE=[CSIZE])
DATA N/2, 4/
DATA INIT/1, 2, 3, 4, 5, 6, 7, 8/
INTEGER :: I
DO WHILE(I <= RSIZE)
IN(I) = INIT(I)
END DO
TYPE(C_PTR) :: PLAN
PLAN = KML_FFT_PLAN_DFT_R2C(RANK, N, IN, OUT, KML_FFT_ESTIMATE)
CALL KML_FFT_EXECUTE_DFT_R2C(PLAN, IN, OUT)
CALL KML_FFT_DESTROY_PLAN(PLAN)
CALL KML_FFT_FREE(PIN)
CALL KML_FFT_FREE(POUT)
!
! OUT = /3.600000E+01, 0.000000E+00, -4.000000E+00, 4.000000E+00,
!        -4.000000E+00, 0.000000E+00, -1.600000E+01, 0.000000E+00,
!        0.000000E+00, 0.000000E+00, 0.000000E+00, 0.000000E+00/
!
```