NEON在Android中的使用举例【转】

转自：http://blog.csdn.net/fengbingchun/article/details/37766607

版权声明：本文为博主原创文章，未经博主允许不得转载。

1、 打开Eclipse，File-->New-->AndroidApplication Project-->Application Name:Hello-Neon, Project Name: Hello-Neon,Package Name:com.hello_neon.Android, Minimum Required SDK:API 9:Android 2.3(Gingerbread),Next-->去掉Create custom launcher icon的勾选，Next-->Next-->ActivityName:Hello_NeonProjectActivity,Finish.

2、 打开Hello-Neon工程下的src-->com.hello_neon.android-->Hello_NeonProjectActivity.Java，将其内容改为：

[java] view plain copy

package com.hello_neon.android;

import android.os.Bundle;

import android.app.Activity;

import android.widget.TextView;

public class Hello_NeonProjectActivity extends Activity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState)

{

super.onCreate(savedInstanceState);

/* Create a TextView and set its content.

* the text is retrieved by calling a native function.

*/

TextView tv = new TextView(this);

tv.setText( stringFromJNI() );

setContentView(tv);

}

/* A native method that is implemented by the

* 'helloneon' native library, which is packaged with this application.

*/

public native String stringFromJNI();

/* this is used to load the 'helloneon' library on application

* startup. The library has already been unpacked into

* /data/data/com.example.neon/lib/libhelloneon.so at

* installation time by the package manager.

*/

static {

System.loadLibrary("helloneon");

}

}

3、 保存Hello_NeonProjectActivity.java文件，打开命令行窗口，将其定位到\bin\classes目录下，输入命令：javah –classpath D:\ProgramFiles\Android\android-sdk\platforms\android-9\android.jar;com.hello_neon.android.Hello_NeonProjectActivity ,会在\bin\classes目录下生成com_hello_neon_android_Hello_NeonProjectActivity.h文件(说明：*.jar也可以是其它版本)；

4、 选中Hello-Neon工程，点击右键-->New-->Folder新建一个jni文件夹，在此文件夹下添加Android.mk、Application.mk、helloneon.c、helloneon-intrinsics.c、helloneon-intrinsics.h五个文件，其中内容分别为：

Android.mk:

[html] view plain copy

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := helloneon

#填写要编译的源文件路径

LOCAL_SRC_FILES := helloneon.c helloneon-intrinsics.c

#默认包含的头文件路径

LOCAL_C_INCLUDES := \

$(LOCAL_PATH) \

$(LOCAL_PATH)/..

#-g 后面的一系列项目添加了才能使用arm_neon-h头文件, -mfloat-abi=softfp -mfpu=neon 使用arm_neon.h必须

LOCAL_CFLAGS := -g -mfloat-abi=softfp -mfpu=neon -march=armv7-a -mtune=cortex-a8

LOCAL_LDLIBS := -lz -llog

TARGET_ARCH_ABI := armeabi-v7a

LOCAL_ARM_MODE := arm

ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)

#采用NEON优化技术

LOCAL_ARM_NEON := true

#LOCAL_CFLAGS := -DHAVE_NEON=1

endif

LOCAL_STATIC_LIBRARIES := cpufeatures

#生成动态调用库

include $(BUILD_SHARED_LIBRARY)

$(call import-module,cpufeatures)

Application.mk:

[html] view plain copy

APP_PROJECT_PATH := $(call my-dir)/..

APP_PLATFORM := android-10

#choose which library to compile against in your Makefile

APP_STL := stlport_static

#APP_ABI这句指定了编译的目标平台类型，可以针对不同平台进行优化,x86 or armeabi-v7a

# Build both ARMv5TE and ARMv7-A machine code.

APP_ABI := armeabi armeabi-v7a

APP_CPPFLAGS += -fexceptions

#for using c++ features,you need to enable these in your Makefile

APP_CPP_FEATURES += exceptions rtti

helloneon.c:

[cpp] view plain copy

#include <jni.h>

#include <time.h>

#include <stdio.h>

#include <stdlib.h>

#include <cpu-features.h>

#include "helloneon-intrinsics.h"

#define DEBUG 0

#define HAVE_NEON

#if DEBUG

#include <android/log.h>

# define D(x...) __android_log_print(ANDROID_LOG_INFO,"helloneon",x)

#else

# define D(...) do {} while (0)

#endif

/* return current time in milliseconds */

static double

now_ms(void)

{

struct timespec res;

clock_gettime(CLOCK_REALTIME, &res);

return 1000.0*res.tv_sec + (double)res.tv_nsec/1e6;

}

/* this is a FIR filter implemented in C */

static void

fir_filter_c(short *output, const short* input, const short* kernel, int width, int kernelSize)

{

int offset = -kernelSize/2;

int nn;

for (nn = 0; nn < width; nn++) {

int sum = 0;

int mm;

for (mm = 0; mm < kernelSize; mm++) {

sum += kernel[mm]*input[nn+offset+mm];

}

output[nn] = (short)((sum + 0x8000) >> 16);

}

}

#define FIR_KERNEL_SIZE 32

#define FIR_OUTPUT_SIZE 2560

#define FIR_INPUT_SIZE (FIR_OUTPUT_SIZE + FIR_KERNEL_SIZE)

#define FIR_ITERATIONS 600

static const short fir_kernel[FIR_KERNEL_SIZE] = {

0x10, 0x20, 0x40, 0x70, 0x8c, 0xa2, 0xce, 0xf0, 0xe9, 0xce, 0xa2, 0x8c, 070, 0x40, 0x20, 0x10,

0x10, 0x20, 0x40, 0x70, 0x8c, 0xa2, 0xce, 0xf0, 0xe9, 0xce, 0xa2, 0x8c, 070, 0x40, 0x20, 0x10 };

static short fir_output[FIR_OUTPUT_SIZE];

static short fir_input_0[FIR_INPUT_SIZE];

static const short* fir_input = fir_input_0 + (FIR_KERNEL_SIZE/2);

static short fir_output_expected[FIR_OUTPUT_SIZE];

/* This is a trivial JNI example where we use a native method

* to return a new VM String. See the corresponding Java source

* file located at:

*

* apps/samples/hello-neon/project/src/com/example/neon/HelloNeon.java

*/

JNIEXPORT jstring JNICALL Java_com_hello_1neon_android_Hello_1NeonProjectActivity_stringFromJNI(JNIEnv *env, jobject thiz)

{

char* str;

uint64_t features;

char buffer[512];

char tryNeon = 0;

double t0, t1, time_c, time_neon;

/* setup FIR input - whatever */

{

int nn;

for (nn = 0; nn < FIR_INPUT_SIZE; nn++) {

fir_input_0[nn] = (5*nn) & 255;

}

fir_filter_c(fir_output_expected, fir_input, fir_kernel, FIR_OUTPUT_SIZE, FIR_KERNEL_SIZE);

}

/* Benchmark small FIR filter loop - C version */

t0 = now_ms();

{

int count = FIR_ITERATIONS;

for (; count > 0; count--) {

fir_filter_c(fir_output, fir_input, fir_kernel, FIR_OUTPUT_SIZE, FIR_KERNEL_SIZE);

}

}

t1 = now_ms();

time_c = t1 - t0;

asprintf(&str, "FIR Filter benchmark:\nC version : %g ms\n", time_c);

strlcpy(buffer, str, sizeof buffer);

free(str);

strlcat(buffer, "Neon version : ", sizeof buffer);

if (android_getCpuFamily() != ANDROID_CPU_FAMILY_ARM) {

strlcat(buffer, "Not an ARM CPU !\n", sizeof buffer);

goto EXIT;

}

features = android_getCpuFeatures();

if ((features & ANDROID_CPU_ARM_FEATURE_ARMv7) == 0) {

strlcat(buffer, "Not an ARMv7 CPU !\n", sizeof buffer);

goto EXIT;

}

/* HAVE_NEON is defined in Android.mk ! */

#ifdef HAVE_NEON

if ((features & ANDROID_CPU_ARM_FEATURE_NEON) == 0) {

strlcat(buffer, "CPU doesn't support NEON !\n", sizeof buffer);

goto EXIT;

}

/* Benchmark small FIR filter loop - Neon version */

t0 = now_ms();

{

int count = FIR_ITERATIONS;

for (; count > 0; count--) {

fir_filter_neon_intrinsics(fir_output, fir_input, fir_kernel, FIR_OUTPUT_SIZE, FIR_KERNEL_SIZE);

}

}

t1 = now_ms();

time_neon = t1 - t0;

asprintf(&str, "%g ms (x%g faster)\n", time_neon, time_c / (time_neon < 1e-6 ? 1. : time_neon));

strlcat(buffer, str, sizeof buffer);

free(str);

/* check the result, just in case */

{

int nn, fails = 0;

for (nn = 0; nn < FIR_OUTPUT_SIZE; nn++) {

if (fir_output[nn] != fir_output_expected[nn]) {

if (++fails < 16)

D("neon[%d] = %d expected %d", nn, fir_output[nn], fir_output_expected[nn]);

}

}

D("%d fails\n", fails);

}

#else /* !HAVE_NEON */

strlcat(buffer, "Program not compiled with ARMv7 support !\n", sizeof buffer);

#endif /* !HAVE_NEON */

EXIT:

return (*env)->NewStringUTF(env, buffer);

}

helloneon-intrinsics.h:

[cpp] view plain copy

#ifndef HELLONEON_INTRINSICS_H

#define HELLONEON_INTRINSICS_H

void fir_filter_neon_intrinsics(short *output, const short* input, const short* kernel, int width, int kernelSize);

#endif /* HELLONEON_INTRINSICS_H */

helloneon-intrinsics.c:

[cpp] view plain copy

#include "helloneon-intrinsics.h"

#include <arm_neon.h>

/* this source file should only be compiled by Android.mk when targeting

* the armeabi-v7a ABI, and should be built in NEON mode

*/

void

fir_filter_neon_intrinsics(short *output, const short* input, const short* kernel, int width, int kernelSize)

{

#if 1

int nn, offset = -kernelSize/2;

for (nn = 0; nn < width; nn++)

{

int mm, sum = 0;

int32x4_t sum_vec = vdupq_n_s32(0);

for(mm = 0; mm < kernelSize/4; mm++)

{

int16x4_t kernel_vec = vld1_s16(kernel + mm*4);

int16x4_t input_vec = vld1_s16(input + (nn+offset+mm*4));

sum_vec = vmlal_s16(sum_vec, kernel_vec, input_vec);

}

sum += vgetq_lane_s32(sum_vec, 0);

sum += vgetq_lane_s32(sum_vec, 1);

sum += vgetq_lane_s32(sum_vec, 2);

sum += vgetq_lane_s32(sum_vec, 3);

if(kernelSize & 3)

{

for(mm = kernelSize - (kernelSize & 3); mm < kernelSize; mm++)

sum += kernel[mm] * input[nn+offset+mm];

}

output[nn] = (short)((sum + 0x8000) >> 16);

}

#else /* for comparison purposes only */

int nn, offset = -kernelSize/2;

for (nn = 0; nn < width; nn++) {

int sum = 0;

int mm;

for (mm = 0; mm < kernelSize; mm++) {

sum += kernel[mm]*input[nn+offset+mm];

}

output[nn] = (short)((sum + 0x8000) >> 16);

}

#endif

}

5、 利用NDK生成.so文件：选中工程-->Properties-->Builders-->New-->选中Program-->OK,Name:Hello_Neon_Builder,Location: D:\ProgramFiles\Android\android-sdk\android-ndk-r9\ndk-build.cmd,Working Directory: E:\NEON\Eclipse\Hello-Neon -->Apply,选中Refresh,勾选Refreshresources upon completion, 勾选Specific resources,点击Specify Resources…,勾选Hello-Neon工程下的libs文件夹，Finish-->Apply,选中BuildOptions,勾选Allocate Console(necessary for input), After a “Clean”, During manualbuilds, During auto builds, Specify working set of relevant resources,点击SpecifyResoures…,勾选Hello-Neon工程下的jni文件夹，Finish-->Apply-->OK-->OK,会在libs文件夹下生成libhelloneon.so文件;

6、 选中Hello-Neon，-->Run As-->AndroidApplication,运行结果为：

FIRFilter benchmark:

C version :282.84 ms

Neon version :135985 ms(x2.07994 faster)

以上是.c文件的操作步骤，若将.c文件该为.cpp文件，则需改动两个文件：

1、将Android.mk改为：

[html] view plain copy

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE := helloneon

#填写要编译的源文件路径

LOCAL_SRC_FILES := helloneon.cpp helloneon-intrinsics.cpp

#默认包含的头文件路径

LOCAL_C_INCLUDES := \

$(LOCAL_PATH) \

$(LOCAL_PATH)/..

#-g 后面的一系列项目添加了才能使用arm_neon-h头文件, -mfloat-abi=softfp -mfpu=neon 使用arm_neon.h必须

LOCAL_CFLAGS := -g -mfloat-abi=softfp -mfpu=neon -march=armv7-a -mtune=cortex-a8

LOCAL_LDLIBS := -lz -llog

TARGET_ARCH_ABI := armeabi-v7a

LOCAL_ARM_MODE := arm

ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)

#采用NEON优化技术

LOCAL_ARM_NEON := true

#LOCAL_CFLAGS := -DHAVE_NEON=1

endif

LOCAL_STATIC_LIBRARIES := cpufeatures

#生成动态调用库

include $(BUILD_SHARED_LIBRARY)

$(call import-module,cpufeatures)

2、helloneon.c改为：

[cpp] view plain copy

#include <jni.h>

#include <time.h>

#include <stdio.h>

#include <stdlib.h>

#include <cpu-features.h>

#include "helloneon-intrinsics.h"

#define DEBUG 0

#define HAVE_NEON

#ifdef __cplusplus

extern "C" {

#endif

#if DEBUG

#include <android/log.h>

# define D(x...) __android_log_print(ANDROID_LOG_INFO,"helloneon",x)

#else

# define D(...) do {} while (0)

#endif

/* return current time in milliseconds */

static double

now_ms(void)

{

struct timespec res;

clock_gettime(CLOCK_REALTIME, &res);

return 1000.0*res.tv_sec + (double)res.tv_nsec/1e6;

}

/* this is a FIR filter implemented in C */

static void

fir_filter_c(short *output, const short* input, const short* kernel, int width, int kernelSize)

{

int offset = -kernelSize/2;

int nn;

for (nn = 0; nn < width; nn++) {

int sum = 0;

int mm;

for (mm = 0; mm < kernelSize; mm++) {

sum += kernel[mm]*input[nn+offset+mm];

}

output[nn] = (short)((sum + 0x8000) >> 16);

}

}

#define FIR_KERNEL_SIZE 32

#define FIR_OUTPUT_SIZE 2560

#define FIR_INPUT_SIZE (FIR_OUTPUT_SIZE + FIR_KERNEL_SIZE)

#define FIR_ITERATIONS 600

static const short fir_kernel[FIR_KERNEL_SIZE] = {

0x10, 0x20, 0x40, 0x70, 0x8c, 0xa2, 0xce, 0xf0, 0xe9, 0xce, 0xa2, 0x8c, 070, 0x40, 0x20, 0x10,

0x10, 0x20, 0x40, 0x70, 0x8c, 0xa2, 0xce, 0xf0, 0xe9, 0xce, 0xa2, 0x8c, 070, 0x40, 0x20, 0x10 };

static short fir_output[FIR_OUTPUT_SIZE];

static short fir_input_0[FIR_INPUT_SIZE];

static const short* fir_input = fir_input_0 + (FIR_KERNEL_SIZE/2);

static short fir_output_expected[FIR_OUTPUT_SIZE];

/* This is a trivial JNI example where we use a native method

* to return a new VM String. See the corresponding Java source

* file located at:

*

* apps/samples/hello-neon/project/src/com/example/neon/HelloNeon.java

*/

JNIEXPORT jstring JNICALL Java_com_hello_1neon_android_Hello_1NeonProjectActivity_stringFromJNI(JNIEnv *env, jobject thiz)

{

char str[512] = {0};

uint64_t features;

char buffer[512];

char tryNeon = 0;

double t0, t1, time_c, time_neon;

/* setup FIR input - whatever */

{

int nn;

for (nn = 0; nn < FIR_INPUT_SIZE; nn++) {

fir_input_0[nn] = (5*nn) & 255;

}

fir_filter_c(fir_output_expected, fir_input, fir_kernel, FIR_OUTPUT_SIZE, FIR_KERNEL_SIZE);

}

/* Benchmark small FIR filter loop - C version */

t0 = now_ms();

{

int count = FIR_ITERATIONS;

for (; count > 0; count--) {

fir_filter_c(fir_output, fir_input, fir_kernel, FIR_OUTPUT_SIZE, FIR_KERNEL_SIZE);

}

}

t1 = now_ms();

time_c = t1 - t0;

sprintf(str, "FIR Filter benchmark:\nC version : %g ms\n", time_c);

strlcpy(buffer, str, sizeof buffer);

strlcat(buffer, "Neon version : ", sizeof buffer);

if (android_getCpuFamily() != ANDROID_CPU_FAMILY_ARM) {

strlcat(buffer, "Not an ARM CPU !\n", sizeof buffer);

goto EXIT;

}

features = android_getCpuFeatures();

if ((features & ANDROID_CPU_ARM_FEATURE_ARMv7) == 0) {

strlcat(buffer, "Not an ARMv7 CPU !\n", sizeof buffer);

goto EXIT;

}

/* HAVE_NEON is defined in Android.mk ! */

#ifdef HAVE_NEON

if ((features & ANDROID_CPU_ARM_FEATURE_NEON) == 0) {

strlcat(buffer, "CPU doesn't support NEON !\n", sizeof buffer);

goto EXIT;

}

/* Benchmark small FIR filter loop - Neon version */

t0 = now_ms();

{

int count = FIR_ITERATIONS;

for (; count > 0; count--) {

fir_filter_neon_intrinsics(fir_output, fir_input, fir_kernel, FIR_OUTPUT_SIZE, FIR_KERNEL_SIZE);

}

}

t1 = now_ms();

time_neon = t1 - t0;

sprintf(str, "%g ms (x%g faster)\n", time_neon, time_c / (time_neon < 1e-6 ? 1. : time_neon));

strlcat(buffer, str, sizeof buffer);

/* check the result, just in case */

{

int nn, fails = 0;

for (nn = 0; nn < FIR_OUTPUT_SIZE; nn++) {

if (fir_output[nn] != fir_output_expected[nn]) {

if (++fails < 16)

D("neon[%d] = %d expected %d", nn, fir_output[nn], fir_output_expected[nn]);

}

}

D("%d fails\n", fails);

}

#else /* !HAVE_NEON */

strlcat(buffer, "Program not compiled with ARMv7 support !\n", sizeof buffer);

#endif /* !HAVE_NEON */

EXIT:

return env->NewStringUTF(buffer);

}

#ifdef __cplusplus

}

#endif

参考文献：

1、 http://blog.csdn.net/fengbingchun/article/details/11580983

2、 android-ndk-r9-windows-x86_64中的hello-neon例子代码