io.kgraph.library.cf

Class Als

java.lang.Object

io.kgraph.library.cf.Als

All Implemented Interfaces:

ComputeFunction<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage>

public class Als
extends Object
implements ComputeFunction<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage>

Alternating Least Squares (ALS) implementation.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	Als.InitItemsComputation This computation class is used to initialize the factors of the item nodes in the second superstep.
class	Als.InitUsersComputation This computation class is used to initialize the factors of the user nodes in the very first superstep, and send the first updates to the item nodes.

Nested classes/interfaces inherited from interface io.kgraph.pregel.ComputeFunction

ComputeFunction.Aggregators, ComputeFunction.Callback<K,VV,EV,Message>, ComputeFunction.InitCallback, ComputeFunction.MasterCallback, ComputeFunction.ReadAggregators, ComputeFunction.ReadWriteAggregators

Field Summary

Fields

Modifier and Type	Field and Description
static String	ITERATIONS Keyword for parameter setting the number of iterations.
static int	ITERATIONS_DEFAULT Default value for ITERATIONS.
static String	LAMBDA Keyword for parameter setting the regularization parameter LAMBDA.
static float	LAMBDA_DEFAULT Default value for LABDA.
static String	RANDOM_SEED Random seed.
static Long	RANDOM_SEED_DEFAULT Default random seed
static String	RMSE_AGGREGATOR Aggregator used to compute the RMSE
static String	RMSE_TARGET RMSE target to reach.
static float	RMSE_TARGET_DEFAULT Default value of RMSE target.
static String	VECTOR_SIZE Keyword for parameter setting the Latent Vector Size.
static int	VECTOR_SIZE_DEFAULT Default value for vector size.

Constructor Summary

Constructors

Constructor and Description
Als()

Method Summary

Modifier and Type	Method and Description
void	compute(int superstep, VertexWithValue<CfLongId,org.jblas.FloatMatrix> vertex, Iterable<FloatMatrixMessage> messages, Iterable<EdgeWithValue<CfLongId,Float>> edges, ComputeFunction.Callback<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage> cb) The function for computing a new vertex value or sending messages to the next superstep.
protected long	getTotalNumEdges(ComputeFunction.ReadAggregators aggregators)
void	init(Map<String,?> configs, ComputeFunction.InitCallback cb) Initialize the ComputeFunction, this is the place to register aggregators.
void	masterCompute(int superstep, ComputeFunction.MasterCallback cb) A function for performing sequential computations between supersteps.
void	preSuperstep(int superstep, ComputeFunction.Aggregators aggregators) Prepare for computation.
void	superstepCompute(int superstep, VertexWithValue<CfLongId,org.jblas.FloatMatrix> vertex, Iterable<FloatMatrixMessage> messages, Iterable<EdgeWithValue<CfLongId,Float>> edges, ComputeFunction.Callback<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage> cb) Main ALS compute method.
protected void	updateValue(org.jblas.FloatMatrix value, org.jblas.FloatMatrix mat_M, org.jblas.FloatMatrix mat_R, float lambda)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.kgraph.pregel.ComputeFunction

postSuperstep

Field Detail

RMSE_TARGET

public static final String RMSE_TARGET

RMSE target to reach.

See Also:

Constant Field Values

RMSE_TARGET_DEFAULT

public static final float RMSE_TARGET_DEFAULT

Default value of RMSE target.

See Also:

Constant Field Values

ITERATIONS

public static final String ITERATIONS

Keyword for parameter setting the number of iterations.

See Also:

Constant Field Values

ITERATIONS_DEFAULT

public static final int ITERATIONS_DEFAULT

Default value for ITERATIONS.

See Also:

Constant Field Values

LAMBDA

public static final String LAMBDA

Keyword for parameter setting the regularization parameter LAMBDA.

See Also:

Constant Field Values

LAMBDA_DEFAULT

public static final float LAMBDA_DEFAULT

Default value for LABDA.

See Also:

Constant Field Values

VECTOR_SIZE

public static final String VECTOR_SIZE

Keyword for parameter setting the Latent Vector Size.

See Also:

Constant Field Values

VECTOR_SIZE_DEFAULT

public static final int VECTOR_SIZE_DEFAULT

Default value for vector size.

See Also:

Constant Field Values

RANDOM_SEED

public static final String RANDOM_SEED

Random seed.

See Also:

Constant Field Values

RANDOM_SEED_DEFAULT

public static final Long RANDOM_SEED_DEFAULT

Default random seed

RMSE_AGGREGATOR

public static final String RMSE_AGGREGATOR

Aggregator used to compute the RMSE

See Also:

Constant Field Values

Constructor Detail

Als

public Als()

Method Detail

preSuperstep

public void preSuperstep(int superstep,
                         ComputeFunction.Aggregators aggregators)

Description copied from interface: ComputeFunction

Prepare for computation. This method is executed exactly once prior to compute() being called for any of the vertices in the partition.

Specified by:

preSuperstep in interface ComputeFunction<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage>

Parameters:

superstep - the superstep

aggregators - the aggregators

superstepCompute

public void superstepCompute(int superstep,
                             VertexWithValue<CfLongId,org.jblas.FloatMatrix> vertex,
                             Iterable<FloatMatrixMessage> messages,
                             Iterable<EdgeWithValue<CfLongId,Float>> edges,
                             ComputeFunction.Callback<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage> cb)

Main ALS compute method.

It updates the current latent vector based on ALS:
A = M * M^T + LAMBDA * N * E
V = M * R
A * U = V, then solve for U

where
R: column vector with ratings by this user
M: item features for items rated by this user with dimensions |F|x|R|
M^T: transpose of M with dimensions |R|x|F|
N: number of ratings of this user
E: identity matrix with dimensions |F|x|F|

Parameters:

superstep - the count of the current superstep

vertex - the current vertex with its value

messages - a Map of the source vertex and the message sent from the previous superstep

edges - the adjacent edges with their values

cb - a callback for setting a new vertex value or sending messages to the next superstep

updateValue

protected void updateValue(org.jblas.FloatMatrix value,
                           org.jblas.FloatMatrix mat_M,
                           org.jblas.FloatMatrix mat_R,
                           float lambda)

init

public final void init(Map<String,?> configs,
                       ComputeFunction.InitCallback cb)

Description copied from interface: ComputeFunction

Initialize the ComputeFunction, this is the place to register aggregators.

Specified by:

init in interface ComputeFunction<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage>

Parameters:

configs - configuration parameters

cb - a callback for registering aggregators

masterCompute

public final void masterCompute(int superstep,
                                ComputeFunction.MasterCallback cb)

Description copied from interface: ComputeFunction

A function for performing sequential computations between supersteps.

Specified by:

masterCompute in interface ComputeFunction<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage>

Parameters:

superstep - the superstep

cb - a callback for writing to aggregators or halting the computation

compute

public void compute(int superstep,
                    VertexWithValue<CfLongId,org.jblas.FloatMatrix> vertex,
                    Iterable<FloatMatrixMessage> messages,
                    Iterable<EdgeWithValue<CfLongId,Float>> edges,
                    ComputeFunction.Callback<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage> cb)

Description copied from interface: ComputeFunction

The function for computing a new vertex value or sending messages to the next superstep.

Specified by:

compute in interface ComputeFunction<CfLongId,org.jblas.FloatMatrix,Float,FloatMatrixMessage>

Parameters:

superstep - the count of the current superstep

vertex - the current vertex with its value

messages - a Map of the source vertex and the message sent from the previous superstep

edges - the adjacent edges with their values

cb - a callback for setting a new vertex value or sending messages to the next superstep

getTotalNumEdges

protected long getTotalNumEdges(ComputeFunction.ReadAggregators aggregators)