How to link OpenBlas for armv7 by CMake in Android Studio?

[nannanmath]

I compile OpenBlas according to https://github.com/xianyi/OpenBLAS/wiki/How-to-build-OpenBLAS-for-Android. I also find a section about linking:https://github.com/xianyi/OpenBLAS/wiki/How-to-build-OpenBLAS-for-Android#linking-openblas-0219-and-earlier-for-armv7. Howerver, I use cmake in Android Studio, I want to know how to set them in CMakeLists.txt. Thanks.

[brada4]

Care to mention it is intellij or eclipse android studio?
You need NDK to build anything from CmakeLists.txt included.
In short - two worlds - 0.2.19 and below - you need old NDK and only hardfp abi is supported, 0.2.20 and in future - any ndk, also softfp ABI is supported (not yet completely up to the speed of other).

[xsacha]

I understand you have already built the library.
Add this to your CMakeLists:

add_library(openblas STATIC IMPORTED)
set_property(TARGET OpenBLAS PROPERTY IMPORTED_LOCATION /path/to/libopenblas.a)
target_link_libraries(${PROJECT_NAME} openblas)

Change STATIC to SHARED if you built OpenBLAS as a shared library.

[martin-frbg]

@nannanmath did xsacha's suggestion solve the problem for you ?

[abhishek-sehgal]

Hi @martin-frbg, I followed xsacha's suggestion but i cannot add cblas.h in my android project. The Library gets added but i cannot access any functions

[xsacha]

target_include_directories(${PROJECT_NAME} PRIVATE /path/to/blasinclude)

[abhishek-sehgal]

This statement is causing External Native Build Issues. I guess the include path might be incorrect, I've tried the following:

OpenBLAS/ OpenBLAS/lapack-netlib/CBLAS/include OpenBLAS/relapack/src

[xsacha]

Well you said you weren't able to find cblas.h in the include, so you just need to add that path.

[abhishek-sehgal]

The following directories have cblas.h in them and I've tried both of them and still the issue persisted
OpenBLAS/

OpenBLAS/lapack-netlib/CBLAS/include

[xsacha]

What's the issue and what's the #include line?

[xsacha]

Usually programs that use BLAS keep their own BLAS headers. It shouldn't need to include anything from openblas. It's a standard API.

[abhishek-sehgal]

In the CMakeLists.txt file I added the target_include_directories as you had mentioned. The path I have added is as follows:

target_include_directories(${PROJECT_NAME} PRIVATE /Users/abhisheksehgal/Desktop/Test/OpenBLAS/lapack-netlib/CBLAS/include)

Now in Android Studio when I try to build the project it causes the gradle sync to fail with the messages saying "External Native Build Issues" at the target_include_directories line in CMakeLists.txt

[Mik-el]

Something is not clear to me guys. (I'm trying to use DLIB with OpenBlas on Android).

• I resulted to compile OpenBlas for Android. (So now I have OpenBlas built files with a Visual Studio solution file inside, OpenBlAS.sln).
• in OpenBLASConfig.cmake I set libopenblas.a as "output" file, as suggested here.

I have two questions:

1. I opened Visual Studio and I fully compiled the OpenBlas solution (ALL_BUILD), but I don't see any generated libopenblas.a file. What am I missing?

2. Will the Dlib shared library (.so) still be compiled by Android studio, and do I have to only add the libopenblas.a path in the Android project, as suggested by @xsacha here . Right?

Thanks in advance.

[brada4]

please do not overtake unrelated threads. Dlib still has no use of any BLAS.
davisking/dlib#2202

[martin-frbg]

hm, I read the old dlib issue as "detecting blas function availability used to be broken in the dlib build but should be fixed now". @Mik-el do you get any compilation errors from Visual Studio, and do you see any libopenblas files built anywhere (maybe it is only doing the shared one by default)?