Currently, many main-stream deep-learning libraries are implemented in C/C++. In order to make Angel parameter server available for these libraries, it is necessary to provide C/C++ interfaces for these libraries to start Angel and call the corresponding interfaces from internal.

Angel is developed with Java, and currently has implemented a basic interface that can start PSAgent, send model delta and get parameters.

• need JNI if called with C
• support multithreading environment; The JNI JavaVM objects can be shared across threads, whereas JNIEnv can't
• abstract out the C version of the PSAgent and MatrixClient classes or interfaces
• PSAgent ensures that each process starts only one instance

The specific interfaces are as follows:

C/C++ Interfaces

PSAgent Initialization and Start-up

1. Initialization

   C++Copy

   	PSAgent psAgent = new PSAgent(conf, masterIp, masterPort, clientIndex);
   	conf:Configuration //Angel system configuration
   	masterIp:String //Angel app master IP address
   	masterPort:int //Angel app master port
   	clientIndex:int //client index (globally unique) 
   

2. Start-up

   C++Copy

   psAgent.initAndStart();
   

Matrix Operations

1. getMatrixClient

   C++Copy

   	MatrixClient matrixClient = psAgent.getMatrixClient(matrixName, taskIndex);
   	matrixName:String
   	taskIndex:int task //index the (globally unique) task execution unit, used by sync control (BSP, SSP)
   

2. Matrix Interfaces

   C++Copy

   	//Set every element in the matrix to a random number
   	public void random(int range) throws Exception;
   
   	//Set every element in the matrix to 0
   	public void zero() throws Exception;
   
   	//Update the matrix
   	public void increment(double[] delta) throws Exception;
   
   	//Update the matrix by index
   	public void increment(int[] indexes, double[] delta) throws Exception;
   
   	//Get the matrix by index
   	public double[] get(int[] indexes) throws Exception;
   
   	//Get the matrix
   	public double[] get() throws Exception;
   
   	//Update the model delta in PSAgent's local cache to PS
   	public Future<VoidResult> flush() throws Exception;
   
   	//Update the model delta in PSAgent's local cache to PS and update the clock
   	public Future<VoidResult> clock() throws Exception;
   
   	//Aggregate UDF, for example, sum, max
   	public AggrResult aggr(AggrFunc func) throws Exception;
   
   	//UDF for matrix updating, for example, scalar, increment
   	public Future<VoidResult> update(UpdaterFunc func) throws Exception;