Tensorflow JNI development

About

Based on Build TensorFlow 2.0 for Java on Windows article. Also this one - tensorflow/java/README.md.

These instructions are for Linux and old TensorFlow 1.15.0.

How to:

• Build TF JNI - libtensorflow.jar, libtensorflow_jni.so and pom.xml
• Add TF JAR to local Maven which will override the Central Maven Repository
• Modify TF JNI functions
• Create Elipse project

There's JavaCPP Presets project. Seems useless.

Install

In Kubuntu:

• Get TensorFlow-1.15.0
• Install bazel 0.25.2

Based on Feeding Tensorflow from GPU.

Build

cd ~/git/tensorflow-1.15.0
./configure # do not forget CUDA
bazel build -c opt //tensorflow/java:tensorflow //tensorflow/java:libtensorflow_jni //tensorflow/java:pom

With TF, bazel tends to rebuild everything from scratch - takes a ton of time. Is it because it gets restarted after idle timeout or something else? A somewhat solution might be

At launch bazel starts its server which, to prevent it, add to ~/.bazelrc:
startup --max_idle_secs=0

Artifacts of interest are in bazel-bin/tensorflow/java/:

libtensorflow_jni.so
libtensorflow.jar
pom.xml

• xml and jar will be taken care of by mvn command.
• so will have to be in the library path - set LD_LIBRARY_PATH or PATH or go "java -Djava.library.path"

Install JAR to local Maven Repository

~$ mvn install:install-file -Dfile=bazel-bin/tensorflow/java/libtensorflow.jar -DpomFile=bazel-bin/tensorflow/java/pom.xml

How to uninstall maven local repo - and switch back to official versions from Maven Central:

https://stackoverflow.com/questions/15358851/how-to-remove-jar-file-from-local-maven-repository-which-was-added-with-install

Modify TF JNI

For example, one wants to create a new function in org.tensorflow.TensorFlow package. Then, see:

tensorflow/java/src/main/java/org/tensorflow/
tensorflow/java/src/main/native/

• add native method to tensorflow/java/src/main/java/org/tensorflow/TensorFlow.java
• add to header file tensorflow/java/src/main/native/tensorflow_jni.h
• add to c file tensorflow/java/src/main/native/tensorflow_jni.cc

• rebuild and reinstall to mvn

Java Maven project in Eclipse

• Create a new maven project
• Edit pom.xml:

<project>
  ...
  <dependencies>
    ...
    <dependency>
      <groupId>org.tensorflow</groupId>
      <artifactId>libtensorflow</artifactId>
      <version>1.15.0</version>
    </dependency>
    ...
  </dependencies>
  ...
</project>

Basic example code

tfhello.java:

import org.tensorflow.TensorFlow;

public class tfhello{
	public static void main(String[] args){
		System.out.println(TensorFlow.version());
	}
}