14.1. FFT 性能测试示例
14.1.1. 概述
本示例演示了 HPM SDK 中不同 FFT 实现方式的性能对比。示例测试了多种 FFT 算法的执行时间和精度，包括 DSP radix-4、DSP radix-2、Q31 DSP radix-2 以及 Q31 FFA FFT（如果支持）。
14.1.2. 功能说明
生成包含三个正弦波的合成信号
测试不同 FFT 实现方式的性能： - DSP radix-4 复数 FFT - DSP radix-2 复数 FFT - Q31 DSP radix-2 复数 FFT - Q31 FFA FFT（如果支持）
验证 FFT 和 IFFT 的精度
测试不同点数（64-1024点）的性能
14.1.3. 硬件要求
测试FFA性能需要支持 FFA 功能的SOC（如 HPM63xx、HPM6Exx、HPM68xx、HPM6Pxx）
14.1.4. 软件要求
HPM SDK
CMake 3.20.0 或更高版本
交叉编译工具链
14.1.5. 构建说明
进入示例目录
创建构建目录并进入
运行 CMake 配置
编译项目
14.1.6. 运行说明
将编译生成的二进制文件烧录到开发板
通过串口查看输出结果
观察不同 FFT 实现方式的性能数据
14.1.7. 输出说明
程序会输出以下信息： - CPU 频率 - 不同 FFT 实现方式的执行时间 - 频率分量的幅度 - 精度验证结果
14.1.8. 注意事项
确保开发板供电正常
确保串口连接正确
观察 LED 状态以确认程序运行状态
不同开发板支持的 FFT 实现方式可能不同
14.1.9. 程序设计
软件生成生成几个幅值和相位不同的正弦波并叠加生成一个波形，然后使用fft变换求出幅频特性数据，最后做ifft回复原始数据， 并比对ifft的数据和fft变换的数据是否相一致。几个正弦波如下所示:
幅值11，频率8
幅值19，频率17
幅值13，频率24
14.1.10. 硬件设置
无特殊设置
14.1.11. 性能优化
segger已经默认开启O3优化
hpm_math默认开启了对CPU Cooley-Tukey算法的计算优化，会增加空间占用
复现本文档测试结果需要使用-DHPM_BUILD_TYPE=ram进行编译，这样可以确保DSP计算例程放置在紧耦合内存中以获得最佳性能。构建命令示例：
cmake -GNinja -DBOARD=hpm6750evkmini -DHPM_BUILD_TYPE=ram ..
14.1.12. 运行现象
当工程正确运行后，串口终端会输出计算的名称，采样点数，以及幅频特性的数据，以及每一个单元的运行时间，并在最后输出PASS或者ERROR NUM.
串口输出如下所示：
dsp fft radix-4 Total samples: 64.
total times:5813 tick.
------------------------------------
DC component amplitude:10.000006.
Frequency:8.000000, Amplitude:11.000008.
Frequency:17.000000, Amplitude:18.999988.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
dsp ifft radix-4 Total samples: 64.
total times:5961 tick.
------------------------------------
dsp fft radix-4 Total samples: 256.
total times:29671 tick.
------------------------------------
DC component amplitude:9.999996.
Frequency:8.000000, Amplitude:11.000002.
Frequency:17.000000, Amplitude:18.999998.
Frequency:24.000000, Amplitude:23.000003.
------------------------------------
dsp ifft radix-4 Total samples: 256.
total times:30220 tick.
------------------------------------
dsp fft radix-4 Total samples: 1024.
total times:144992 tick.
------------------------------------
DC component amplitude:9.999997.
Frequency:8.000000, Amplitude:11.000000.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
dsp ifft radix-4 Total samples: 1024.
total times:147161 tick.
------------------------------------
**************************************
dsp fft radix-2 Total samples: 64.
total times:9280 tick.
------------------------------------
DC component amplitude:10.000006.
Frequency:8.000000, Amplitude:11.000008.
Frequency:17.000000, Amplitude:18.999988.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
dsp ifft radix-2 Total samples: 64.
total times:9544 tick.
------------------------------------
dsp fft radix-2 Total samples: 128.
total times:21119 tick.
------------------------------------
DC component amplitude:9.999998.
Frequency:8.000000, Amplitude:11.000001.
Frequency:17.000000, Amplitude:18.999996.
Frequency:24.000000, Amplitude:23.000003.
------------------------------------
dsp ifft radix-2 Total samples: 128.
total times:21575 tick.
------------------------------------
dsp fft radix-2 Total samples: 256.
total times:47643 tick.
------------------------------------
DC component amplitude:9.999996.
Frequency:8.000000, Amplitude:11.000002.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:23.000003.
------------------------------------
dsp ifft radix-2 Total samples: 256.
total times:48582 tick.
------------------------------------
dsp fft radix-2 Total samples: 512.
total times:106047 tick.
------------------------------------
DC component amplitude:9.999997.
Frequency:8.000000, Amplitude:11.000000.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:22.999998.
------------------------------------
dsp ifft radix-2 Total samples: 512.
total times:108005 tick.
------------------------------------
dsp fft radix-2 Total samples: 1024.
total times:234172 tick.
------------------------------------
DC component amplitude:9.999997.
Frequency:8.000000, Amplitude:11.000000.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
dsp ifft radix-2 Total samples: 1024.
total times:237975 tick.
------------------------------------
**************************************
dsp fft q31 radix-2 Total samples: 64.
total times:3782 tick.
------------------------------------
DC component amplitude:10.000006.
Frequency:8.000000, Amplitude:11.000009.
Frequency:17.000000, Amplitude:18.999988.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
dsp ifft q31 radix-2 Total samples: 64.
total times:4220 tick.
------------------------------------
dsp fft q31 radix-2 Total samples: 128.
total times:8252 tick.
------------------------------------
DC component amplitude:9.999998.
Frequency:8.000000, Amplitude:11.000002.
Frequency:17.000000, Amplitude:18.999996.
Frequency:24.000000, Amplitude:23.000003.
------------------------------------
dsp ifft q31 radix-2 Total samples: 128.
total times:9274 tick.
------------------------------------
dsp fft q31 radix-2 Total samples: 256.
total times:17995 tick.
------------------------------------
DC component amplitude:9.999995.
Frequency:8.000000, Amplitude:11.000002.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:23.000005.
------------------------------------
dsp ifft q31 radix-2 Total samples: 256.
total times:20619 tick.
------------------------------------
dsp fft q31 radix-2 Total samples: 512.
total times:39039 tick.
------------------------------------
DC component amplitude:9.999995.
Frequency:8.000000, Amplitude:11.000001.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
dsp ifft q31 radix-2 Total samples: 512.
total times:45407 tick.
------------------------------------
dsp fft q31 radix-2 Total samples: 1024.
total times:85195 tick.
------------------------------------
DC component amplitude:9.999995.
Frequency:8.000000, Amplitude:11.000002.
Frequency:17.000000, Amplitude:19.000003.
Frequency:24.000000, Amplitude:23.000001.
------------------------------------
dsp ifft q31 radix-2 Total samples: 1024.
total times:99603 tick.
------------------------------------
**************************************
Software fft cooley tukey Total samples: 64.
total times:14493 tick.
------------------------------------
DC component amplitude:10.000006.
Frequency:8.000000, Amplitude:11.000014.
Frequency:17.000000, Amplitude:18.999998.
Frequency:24.000000, Amplitude:23.000019.
------------------------------------
Software fft cooley tukey Total samples: 128.
total times:29009 tick.
------------------------------------
DC component amplitude:9.999998.
Frequency:8.000000, Amplitude:11.000004.
Frequency:17.000000, Amplitude:19.000003.
Frequency:24.000000, Amplitude:23.000015.
------------------------------------
Software fft cooley tukey Total samples: 256.
total times:61116 tick.
------------------------------------
DC component amplitude:9.999996.
Frequency:8.000000, Amplitude:11.000000.
Frequency:17.000000, Amplitude:18.999998.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
Software fft cooley tukey Total samples: 512.
total times:131520 tick.
------------------------------------
DC component amplitude:9.999997.
Frequency:8.000000, Amplitude:10.999999.
Frequency:17.000000, Amplitude:19.000001.
Frequency:24.000000, Amplitude:23.000000.
------------------------------------
Software fft cooley tukey Total samples: 1024.
total times:285106 tick.
------------------------------------
DC component amplitude:9.999997.
Frequency:8.000000, Amplitude:10.999997.
Frequency:17.000000, Amplitude:19.000000.
Frequency:24.000000, Amplitude:22.999996.
------------------------------------
**************************************
------------------------------------
convert data from float to q31, nums:128.
total times:3163 tick.
convert data from q31 to float, nums:128.
total times:1177 tick.
------------------------------------
------------------------------------
convert data from float to q31, nums:256.
total times:6225 tick.
convert data from q31 to float, nums:256.
total times:2325 tick.
------------------------------------
------------------------------------
convert data from float to q31, nums:512.
total times:12269 tick.
convert data from q31 to float, nums:512.
total times:4629 tick.
------------------------------------
------------------------------------
convert data from float to q31, nums:1024.
total times:24395 tick.
convert data from q31 to float, nums:1024.
total times:9237 tick.
------------------------------------
------------------------------------
convert data from float to q31, nums:2048.
total times:47949 tick.
convert data from q31 to float, nums:2048.
total times:18453 tick.
------------------------------------
PASS.
性能如下表所示：
采样点 |
64 |
128 |
256 |
512 |
1024 |
|---|---|---|---|---|---|
DSP radix-4（fpu） |
5900 |
N |
29869 |
N |
145366 |
DSP radix-2（fpu） |
9345 |
21220 |
47762 |
106211 |
234534 |
DSP radix-2（Q31） |
4378 |
9581 |
21177 |
46126 |
101331 |
FFAQ31 |
2729 |
4923 |
7769 |
18999 |
N |
CPU（Cooley-Tukey） |
14495 |
29171 |
61176 |
131084 |
283441 |
DSP radix-4（fpu） |
6016 |
N |
30384 |
N |
147651 |
DSP radix-2（fpu） |
9558 |
21632 |
48733 |
108296 |
238775 |
DSP radix-2（Q31） |
4641 |
10301 |
22980 |
50645 |
111359 |
FFAQ31 |
2687 |
4898 |
9152 |
18956 |
N |
Q31 to Float |
1208 |
2392 |
4757 |
9493 |
18965 |
Float to Q31 |
5517 |
10958 |
21970 |
44022 |
88055 |