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：
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:
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)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
#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:
#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 */
#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：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)#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
NEON在Android中的使用举例,布布扣,bubuko.com
原文：http://blog.csdn.net/fengbingchun/article/details/37766607