# The program using the opencv lib which I build from source runs slower than that using libopencv\_java4.so

**URL:** <https://forum.opencv.org/t/the-program-using-the-opencv-lib-which-i-build-from-source-runs-slower-than-that-using-libopencv-java4-so/6421>\
**Category:** C++\
**Tags:** build\
**Created:** [November 25, 2021, 7:02am UTC](https://forum.opencv.org/t/the-program-using-the-opencv-lib-which-i-build-from-source-runs-slower-than-that-using-libopencv-java4-so/6421 "2021-11-25T07:02:00Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![zhttp](https://avatars.discourse-cdn.com/v4/letter/z/a183cd/32.png) [@zhttp](https://forum.opencv.org/u/zhttp)\
**Post date:** [November 25, 2021, 7:02am UTC](https://forum.opencv.org/t/the-program-using-the-opencv-lib-which-i-build-from-source-runs-slower-than-that-using-libopencv-java4-so/6421/1 "2021-11-25T07:02:00Z")

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I got opencv android sdk and opencv source code from [[opencv releases]](https://opencv.org/releases/), and get libopencv\_java4.so from sdk, and build opencv lib from source code using command below (use android ndk):

```auto
cmake -DCMAKE_BUILD_TYPE=Release -DANDROID_TOOLCHAIN=clang -DANDROID_STL=c++_shared -DBUILD_SHARED_LIBS=ON -DANDROID_ABI=arm64-v8a -DINSTALL_ANDROID_EXAMPLES=OFF -DANDROID_EXAMPLES_WITH_LIBS=OFF -DBUILD_EXAMPLES=OFF -DBUILD_DOCS=OFF -DWITH_OPENCL=ON -DCMAKE_TOOLCHAIN_FILE=${ANDROID_NDK}/build/cmake/android.toolchain.cmake -DENABLE_CXX11=ON -DANDROID_SDK_TARGET=23 -DANDROID_NATIVE_API_LEVEL=23 -DANDROID_SDK=${ANDROID_SDK} -DANDROID_NDK=${ANDROID_NDK} -DBUILD_ANDROID_PROJECTS=OFF ../opencv-4.5.4

```

sum up, I have two libs, one of them is libopencv\_java.so from opencv\_android\_sdk(let’s name it as lib1), another one is a couple of libopencv\_\*.so which built from source code(let’s name it as lib2) .

in addition， I build opencv from source code because I want to enable opencl.

in my project, I use cv::UMat to implement may algorithm, when I switch lib1 to lib2, I found my program become much more slower.  
So, my question is there are any difference between lib1 and lib2?

I’m not native English speaker, I apologize if my description is confusing and please let me know, I will explain more.

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<div class="post-metadata">

**Author:** ![zhttp](https://avatars.discourse-cdn.com/v4/letter/z/a183cd/32.png) [@zhttp](https://forum.opencv.org/u/zhttp)\
**Post date:** [November 29, 2021, 10:30am UTC](https://forum.opencv.org/t/the-program-using-the-opencv-lib-which-i-build-from-source-runs-slower-than-that-using-libopencv-java4-so/6421/2 "2021-11-29T10:30:29Z")

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After few days research, I found that the problem is that TBB is not enabled in lib2, lib2 take pthreads as it’s Parallel framework and pthreads is slower than TBB( I don’t know why! ), I add the option “-DWITH-TBB=ON” into cmake options, finally, lib2 works as well as lib1.  
In addition, I use the cmake command below:

```auto
cmake -DCMAKE_BUILD_TYPE=Release -DANDROID_TOOLCHAIN=clang -DANDROID_STL=c++_static -DBUILD_SHARED_LIBS=OFF -DANDROID_ABI="arm64-v8a" -DINSTALL_ANDROID_EXAMPLES=OFF -DANDROID_EXAMPLES_WITH_LIBS=OFF -DBUILD_EXAMPLES=OFF -DBUILD_DOCS=OFF -DWITH_OPENCL=ON -DCMAKE_TOOLCHAIN_FILE=${ANDROID_NDK}/build/cmake/android.toolchain.cmake -DENABLE_CXX11=ON -DANDROID_SDK_TARGET=23 -DANDROID_NATIVE_API_LEVEL=21 -DANDROID_SDK=${ANDROID_SDK} -DANDROID_NDK=${ANDROID_NDK} -DBUILD_ANDROID_EXAMPLES=OFF -DANDROID_PROJECTS_BUILD_TYPE=GRADLE -DBUILD_ANDROID_PROJECTS=OFF -DBUILD_opencv_java=ON -DANT_EXECUTABLE=/root/ant/apache-ant-1.10.12/bin/ant.bat ../opencv-4.5.4

```