Help with integrating Stockfish with android application (Kotlin or Java)

[seekkii]

Hello, I have created a share library file named libstockfish.so with all the executables downloaded from the official website by syncing Cmakelist,txt with graddle. I put the shared library inside appropriate architecture folders, arm64-v8a, armeabi-v7a, x86, x86_64, the compiler was able to recognize the file and I managed to load it without any exception:

val file = File( applicationContext.applicationInfo.nativeLibraryDir + "/libstockfish.so")
var process: Process? = null
try {
        process = Runtime.getRuntime().exec(file.path)
} catch (e: IOException) {
            e.printStackTrace()
}

Then I make a thread that handle command lines which will be passed and write it to line:

 val outThread = Thread(Runnable {
            val processOut = process ?: return@Runnable
            val scanner = Scanner(processOut.inputStream)
            try {
                while (scanner.hasNextLine()) {
                    val line = scanner.nextLine()
                    Log.d("MainActivity", "Received output: $line")
                }
            } catch (e: IOException) {
                Log.e("MainActivity", "Error reading output", e)
            } finally {
                scanner.close()
            }
        })

Then I start the thread and pass the command in by writing to the thread outputstream, but the received result from process.inputstream is null.

 outThread.start()
 var command = "uci\n"
        try{
            if (process != null) {
                process.outputStream.write(command.toByteArray())
                process.outputStream.flush()
            }
        }
        catch (e: IOException) { }

So I would like to ask if this behavior is expected? ,or am I doing something wrong? , any help will be greatly appreciated!

[Disservin]

Eh i dont know any java but looking at this makes me wonder why you write to outputstream ? You have to write to stdin and stockfish's output will be stdout. There's some small documentation on how to interact with Stockfish from your own app.
https://github.com/official-stockfish/Stockfish/wiki/Stockfish-FAQ#how-can-i-use-stockfish-in-my-own-software-application

[seekkii]

Hello, thank you a lot for the reply!
Process.outputstream is actually the outputstream connected to the input of the subprocess, so writing to it should be similar to writing to stdin of the process, if I'm not mistaken, and reading from the process.inputstream should be similar to reading from stdout of the process.

[dav1312]

Since I don't think there are many Android developers here, you might want to take a look at how other developers did it

• Droidfish app: https://github.com/peterosterlund2/droidfish
• Java examples: https://github.com/search?q=stockfish+lang%3AJava&type=code
• Kotlin examples: https://github.com/search?q=stockfish+lang%3AKotlin+&type=code

[wikbpjwstk]

hello, haw you create libstockfish.so. I have problem with it. can you help?

[seekkii]

Hello, depends on what you are using, but there are 2 options for me
Download stockfish
Navigate to the folder contains src and run make as how they instruct you( Keep in mind that they have different options for different platforms)
After make is finished you should see a bunch of .o
run g++ libstockfish.so evaluate.o ....... all the .o here

If you use android studio:
+Create native c++ project, specify c++17 if you use the latest stockfish source code
+Put Stockfish src inside cpp folder
+In Cmakelist.txt
add_library{stockfish evaluate.cpp evaluate.h..... all the excutable here, don't include any nnue related file if you don't need it}
If you need nnue however add this under add_library:
add_custom_target(
copy_nnue_file ALL
DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/nn-ad9b42354671.nnue
)
add_dependencies(stockfish copy_nnue_file)
+In graddle.build
Add this to your android{
sourceSets {
main {
jniLibs.srcDirs = ['libs']
}
}

   externalNativeBuild {
    cmake {
        // Specifies the path to your CMake build script (CMakeLists.txt).
        path "src/main/cpp/CMakeLists.txt"
    }
}
And this to your dependency{
       implementation fileTree(dir: "libs", include: ["*.jar", "*.so"])

+In manifest
<application
android:extractNativeLibs="true"
............

Build->Build apk->locate, change apk to zip, open it and you should see a lib folder that contains 4 folders, libstockfish.so for each of the architecture is inside.

[wikbpjwstk]

I tried to do everything as in the manual. the build process compiles but no *.so files are generated. someone can help more.I tried to do everything as in the manual. the build process compiles but no *.so files are generated. someone can help more.

build.gradle
plugins {
id 'com.android.application'
}

android {
namespace 'com.example.stockfish'
compileSdk 33

defaultConfig {
    applicationId "com.example.stockfish"
    minSdk 29
    targetSdk 33
    versionCode 1
    versionName "1.0"

    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    externalNativeBuild {
        cmake {

            cppFlags '-std=c++17'

        }
    }

    sourceSets {
        main {
            jniLibs.srcDirs = ['libs']
        }
    }
}

buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    }
}
compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}
externalNativeBuild {
    cmake {
        path file('src/main/cpp/CMakeLists.txt')

        version '3.22.1'
    }
}
buildFeatures {
    viewBinding true
}

}

dependencies {

implementation 'androidx.appcompat:appcompat:1.6.1'
implementation 'com.google.android.material:material:1.9.0'
implementation fileTree(dir: "libs", include: ["*.jar", "*.so"])
implementation 'androidx.constraintlayout:constraintlayout:2.1.4'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.5'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'

}

CMAKE

For more information about using CMake with Android Studio, read the

documentation: https://d.android.com/studio/projects/add-native-code.html

Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.22.1)

Declares and names the project.

project("stockfish")

Creates and names a library, sets it as either STATIC

or SHARED, and provides the relative paths to its source code.

You can define multiple libraries, and CMake builds them for you.

Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
stockfish

    # Sets the library as a shared library.

SHARED

    # Provides a relative path to your source file(s).
    benchmark.cpp
    bitbase.cpp
    bitboard.cpp
    bitboard.h
    CMakeLists.txt
    endgame.cpp
    endgame.h
    evaluate.cpp
    evaluate.h
    main.cpp
    material.cpp
    material.h
    misc.cpp
    misc.h
    movegen.cpp
    movegen.h
    movepick.cpp
    movepick.h
    pawns.cpp
    pawns.h
    position.cpp
    position.h
    psqt.cpp
    psqt.h
    search.cpp
    search.h
    thread.cpp
    thread.h
    thread_win32_osx.h
    timeman.cpp
    timeman.h
    tt.cpp
    tt.h
    tune.cpp
    tune.h
    types.h
    uci.cpp
    uci.h
    ucioption.cpp)

add_custom_target(
copy_nnue_file ALL
DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/nn-ad9b42354671.nnue
)
add_dependencies(stockfish copy_nnue_file)

Searches for a specified prebuilt library and stores the path as a

variable. Because CMake includes system libraries in the search path by

default, you only need to specify the name of the public NDK library

you want to add. CMake verifies that the library exists before

completing its build.

find_library( # Sets the name of the path variable.
log-lib

    # Specifies the name of the NDK library that
    # you want CMake to locate.
    log)

Specifies libraries CMake should link to your target library. You

can link multiple libraries, such as libraries you define in this

build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
stockfish

    # Links the target library to the log library
    # included in the NDK.
    ${log-lib})

[wikbpjwstk]

i have this issue

ninja: error: 'nn-ad9b42354671.nnue', needed by 'CMakeFiles/copy_nnue_file', missing and no known rule to make it

[Jochengehtab]

Hello @seekkii can you pleas describe more Detail how i can use the nnue when i am compiling it with CMake. Thanks a lot

[wikbpjwstk]

and after :
add_custom_target(
copy_nnue_file ALL
DEPENDS ${PROJECT_SOURCE_DIR}/incbin/nn-ad9b42354671.nnue
)
add_dependencies(stockfish copy_nnue_file)

[wikbpjwstk]

and after :::::

add_custom_target(
copy_nnue_file ALL
DEPENDS ${PROJECT_SOURCE_DIR}/incbin/nn-ad9b42354671.nnue
)
add_dependencies(stockfish copy_nnue_file)

C/C++: :6:9: error: Could not find incbin file 'nn-ad9b42354671.nnue'
C/C++: .incbin "nn-ad9b42354671.nnue"
C/C++: ^
C/C++: 1 error generated.

[seekkii]

you should copy the nn-ad9b42354671.nnue into cbin folder before running those if you want to use nnue. There should be a lib folder when you inspect your apk, but if not go to app/.cxx/debug/something/, inside there are 4 folders (arm64v8a, armaebiv7a, x86, x86_64, in each of them find stockfish.dir inside cmakefile, change their name to libstockfish.so, before copying those 4 files(arm64v8a....) into your libs folder in app/libs.

[wikbpjwstk]

This not working. I have this stockfish.dir directory but i need file with extension .so . What to do?

[seekkii]

rename it to libstockfish.so add dependency dependencies {other dependencies...... implementation fileTree(dir: 'libs', include: '*.so')

[wikbpjwstk]

@seekkii how to do it without this nnue file?

[seekkii]

I didn't try using graddle to exclude nnue file but i assume you should remove every nnue related file inside add_library{} tag, if there is nnue related stuff inside some part of the src code you might need to comment them as well.

Alternatively just do something like g++ libstockfish.so evaluate.o blah.o blah.o, remember to exclude the nnue related files though

[wikbpjwstk]

I close my question and i solved problems