如何使用android-ndk优化本机代码(速度优化) [英] How to optimize a native code with android-ndk (Speed Optimization)

问题描述

我正在使用cygwin和Windows7编译本机代码. 我在互联网上有很多优化技巧.

I'm compiling a native code using cygwin and Windows7. I got many optimization tips on Internet.

APP_OPTIM := release
ndk-build NDK_DEBUG=0
-DNDEBUG
LOCAL_CFLAGS += -O2

但是我无法完全理解如何在Application.mk和Android.mk上进行设置. 通过应用以上技巧，我尝试了很多情况. 但是，我不认为该优化会在我的本机代码中应用.

But I can't understand exactly how to set these on Application.mk and Android.mk. I tried many cases by applying the above tips. but, I don't think that the optimization is applied in my native code.

Application.mk

Application.mk

APP_PROJECT_PATH := $(shell pwd)
APP_MODULES := native_lib
APP_OPTIM := release
APP_BUILD_SCRIPT := Android.mk
APP_ABI := armeabi

Android.mk

Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := crypto
LOCAL_SRC_FILES := lib/libcrypto.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := native_lib
LOCAL_SRC_FILES := nativeC.c \
                   AES/main.c \
                   AES/aes.c \  

LOCAL_C_INCLUDES := ./lib                  
LOCAL_SHARED_LIBRARIES := crypto
LOCAL_CFLAGS += -O2
LOCAL_CFLAGS += -march=armv6 -marm -mfloat-abi=softfp -mfpu=vfp
LOCAL_LDLIBS += -ldl
include $(BUILD_SHARED_LIBRARY)

我希望有很多评论.

此外，

首先，我尝试比较带有上述标志和不带有上述标志的情况. (例如，我使用Application.mk中的APP_OPTIM:=版本编译了程序，然后又没有它或使用APP_OPTIM:= debug进行了编译.)但是，我看不到运行速度的任何变化.

First, I tried to compare the cases between with the above flag and without it. (e.g. I compiled my program with APP_OPTIM := release in Application.mk, and then I compiled without it or with APP_OPTIM := debug, again.) But, I cannot see any change of the running speed.

第二，这是最重要的，我的程序比较了两个模块的速度. (为方便起见，我将它们称为模块A，B).模块A是预先构建的(在Android.mk中为libcrypto.so).我想将优化应用于模块B.首先，我比较了PC中模块A和B的速度测试(Visual Studio 2010).当我在PC上尝试模块A和B时，模块B的速度比A快.(当然，我已对模块A进行了预编译，并通过调用库来使用它.)现在，我将PC的程序移植到其中了.适用于Android.但是在Android中，模块B比A慢.

Second, this is the most important, My program compare the speed of two modules. (For convenience, I call them module A, B) Module A is prebuilt (which is libcrypto.so in Android.mk). And I want to apply optimization into Module B. First of all, I compared the speed test of module A and B in PC (Visual Studio 2010). When I tried module A and B in the PC, the module B is faster than A. (Of course, I precompiled the module A and I use it by calling the library.) Now I'm porting the my program for PC into it for Android. But in Android, the module B is too slower than A.

因此，我得出结论，这是没有优化的.

Therefore, I concluded that this is not optimized.

总之，

1. 我比较了带有标志和没有标志之间的速度.
2. 在PC上运行此程序时，预编译的模块A的速度比 B，但是在Android中，这是完全相反的.

1. I compared the speed between with the flag and without it.
2. When running this program in PC, the precompiled module A is faster than B, But in Android, it's totally opposite.

您认为我程序的问题是什么吗?预先谢谢你.

Do you thnk what my program's problem is ? Thank you in advance.

推荐答案

APP_OPTIM:=发布

将行APP_OPTIM := release放入您的Application.mk文件

Put the line APP_OPTIM := release into your Application.mk file

ndk-build NDK_DEBUG = 0

只需将NDK_DEBUG=0作为参数传递给ndk-build脚本.定义APP_OPTIM := release后就不需要它.

Just pass the NDK_DEBUG=0 as a parameter to ndk-build script. You don't need it once you define APP_OPTIM := release.

-DNDEBUG

这应该进入您的LOCAL_CFLAGS:

LOCAL_CFLAGS += -DNDEBUG

LOCAL_CFLAGS + = -O2

这实际上不是必需的，因为Android NDK已经定义了-O2优化.

This is not required actually, since the Android NDK already defines -O2 optimization.

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