Example usage for org.apache.mahout.math.function Functions chain

Introduction

In this page you can find the example usage for org.apache.mahout.math.function Functions chain.

Prototype

public static IntIntFunction chain(final DoubleFunction g, final IntIntFunction h) 

Source Link

Document

Constructs the function g( h(a) ).

Usage

From source file:org.carrot2.matrix.factorization.LocalNonnegativeMatrixFactorization.java

License:Open Source License

public void compute() {
    // Prototype Matlab code for the LNMF
    //        /*  w ww.  j a  v a 2 s .  c  o  m*/
    // function [U, V, C] = lnmf(A)
    // [m, n] = size(A);
    // k = 2; % the desired number of base vectors
    // maxiter = 50; % the number of iterations
    // eps = 1e-9; % machine epsilon
    //        
    // U = rand(m, k); % initialize U randomly
    // V = rand(n, k); % initialize V randomly
    // O = ones(m, m); % a matrix of ones
    //        
    // for iter = 1:maxiter
    // V = sqrt( V .* (((A+eps) ./ (U*V'+eps))' * U)); % update V
    // U = U .* (((A+eps)./(U*V'+eps)) * V); % update U
    // U = U ./ (O * U); % normalise U's columns
    // C(1, iter) = norm((A-U*V'), 'fro'); % approximation quality
    // end
    //

    double eps = 1e-9;

    // Seed U and V with initial values
    U = new DenseDoubleMatrix2D(A.rows(), k);
    V = new DenseDoubleMatrix2D(A.columns(), k);
    seedingStrategy.seed(A, U, V);

    // Temporary matrices
    DoubleMatrix2D Aeps = A.copy();
    Aeps.assign(Functions.plus(eps));
    DoubleMatrix2D UV = new DenseDoubleMatrix2D(A.rows(), A.columns());
    DoubleMatrix2D VT = new DenseDoubleMatrix2D(A.columns(), k);
    DoubleMatrix2D UT = new DenseDoubleMatrix2D(A.rows(), k);
    double[] work = new double[U.columns()];

    // Colt functions
    DoubleDoubleFunction invDiv = Functions.swapArgs(Functions.DIV);
    DoubleDoubleFunction sqrtMult = Functions.chain(Functions.SQRT, Functions.MULT);
    DoubleFunction plusEps = Functions.plus(eps);

    if (stopThreshold >= 0) {
        updateApproximationError();
    }

    for (int i = 0; i < maxIterations; i++) {
        // Update V
        U.zMult(V, UV, 1, 0, false, true); // UV <- U*V'
        UV.assign(plusEps); // UV <- UV + eps
        UV.assign(Aeps, invDiv); // UV <- Aeps ./ UV
        UV.zMult(U, VT, 1, 0, true, false); // VT <- UV' * U
        V.assign(VT, sqrtMult); // V <- sqrt(V .* VT)

        // Update U
        U.zMult(V, UV, 1, 0, false, true); // UV <- U*V'
        UV.assign(plusEps); // UV <- UV + eps
        UV.assign(Aeps, invDiv); // UV <- Aeps ./ UV
        UV.zMult(V, UT, 1, 0, false, false); // UT <- UV * V
        U.assign(UT, Functions.MULT); // U <- U .* UT

        MatrixUtils.normalizeColumnL1(U, work);

        iterationsCompleted++;
        if (stopThreshold >= 0) {
            if (updateApproximationError()) {
                break;
            }
        }
    }

    if (ordered) {
        order();
    }
}

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