Exemplo n.º 1
0
 public void setSolverType(SolverType solverType)
 {
     if (solverType == null)
     {
         throw new ArgumentException("solver type must not be null");
     }
     this.solverType = solverType;
 }
Exemplo n.º 2
0
 public Parameter(SolverType solver, double C, double eps) : this(solver, C, eps, 0.1)
 {
 }
Exemplo n.º 3
0
        /**
         * A coordinate descent algorithm for
         * L1-loss and L2-loss SVM dual problems
         *<pre>
         *  min_\alpha  0.5(\alpha^T (Q + D)\alpha) - e^T \alpha,
         *    s.t.      0 <= \alpha_i <= upper_bound_i,
         *
         *  where Qij = yi yj xi^T xj and
         *  D is a diagonal matrix
         *
         * In L1-SVM case:
         *     upper_bound_i = Cp if y_i = 1
         *      upper_bound_i = Cn if y_i = -1
         *      D_ii = 0
         * In L2-SVM case:
         *      upper_bound_i = INF
         *      D_ii = 1/(2*Cp) if y_i = 1
         *      D_ii = 1/(2*Cn) if y_i = -1
         *
         * Given:
         * x, y, Cp, Cn
         * eps is the stopping tolerance
         *
         * solution will be put in w
         *
         * See Algorithm 3 of Hsieh et al., ICML 2008
         *</pre>
         */
        private static void solve_l2r_l1l2_svc(Problem prob, double[] w, double eps, double Cp, double Cn, SolverType solver_type)
        {
            int l = prob.l;
            int w_size = prob.n;
            int i, s, iter = 0;
            double C, d, G;
            double[] QD = new double[l];
            int max_iter = 1000;
            int[] index = new int[l];
            double[] alpha = new double[l];
            sbyte[] y = new sbyte[l];
            int active_size = l;

            // PG: projected gradient, for shrinking and stopping
            double PG;
            double PGmax_old = Double.PositiveInfinity;
            double PGmin_old = Double.NegativeInfinity;
            double PGmax_new, PGmin_new;

            // default solver_type: L2R_L2LOSS_SVC_DUAL
            double[] diag = new[] { 0.5 / Cn, 0, 0.5 / Cp };
            double[] upper_bound = new double[] { Double.PositiveInfinity, 0, Double.PositiveInfinity };
            if (solver_type.getId() == SolverType.L2R_L1LOSS_SVC_DUAL)
            {
                diag[0] = 0;
                diag[2] = 0;
                upper_bound[0] = Cn;
                upper_bound[2] = Cp;
            }

            for (i = 0; i < l; i++)
            {
                if (prob.y[i] > 0)
                {
                    y[i] = +1;
                }
                else
                {
                    y[i] = -1;
                }
            }

            // Initial alpha can be set here. Note that
            // 0 <= alpha[i] <= upper_bound[GETI(i)]
            for (i = 0; i < l; i++)
                alpha[i] = 0;

            for (i = 0; i < w_size; i++)
                w[i] = 0;
            for (i = 0; i < l; i++)
            {
                QD[i] = diag[GETI(y, i)];

                foreach (Feature xi in prob.x[i])
                {
                    double val = xi.Value;
                    QD[i] += val * val;
                    w[xi.Index - 1] += y[i] * alpha[i] * val;
                }
                index[i] = i;
            }

            while (iter < max_iter)
            {
                PGmax_new = Double.NegativeInfinity;
                PGmin_new = Double.PositiveInfinity;

                for (i = 0; i < active_size; i++)
                {
                    int j = i + random.Next(active_size - i);
                    swap(index, i, j);
                }

                for (s = 0; s < active_size; s++)
                {
                    i = index[s];
                    G = 0;
                    sbyte yi = y[i];

                    foreach (Feature xi in prob.x[i])
                    {
                        G += w[xi.Index - 1] * xi.Value;
                    }
                    G = G * yi - 1;

                    C = upper_bound[GETI(y, i)];
                    G += alpha[i] * diag[GETI(y, i)];

                    PG = 0;
                    if (alpha[i] == 0)
                    {
                        if (G > PGmax_old)
                        {
                            active_size--;
                            swap(index, s, active_size);
                            s--;
                            continue;
                        }
                        else if (G < 0)
                        {
                            PG = G;
                        }
                    }
                    else if (alpha[i] == C)
                    {
                        if (G < PGmin_old)
                        {
                            active_size--;
                            swap(index, s, active_size);
                            s--;
                            continue;
                        }
                        else if (G > 0)
                        {
                            PG = G;
                        }
                    }
                    else
                    {
                        PG = G;
                    }

                    PGmax_new = Math.Max(PGmax_new, PG);
                    PGmin_new = Math.Min(PGmin_new, PG);

                    if (Math.Abs(PG) > 1.0e-12)
                    {
                        double alpha_old = alpha[i];
                        alpha[i] = Math.Min(Math.Max(alpha[i] - G / QD[i], 0.0), C);
                        d = (alpha[i] - alpha_old) * yi;

                        foreach (Feature xi in prob.x[i])
                        {
                            w[xi.Index - 1] += d * xi.Value;
                        }
                    }
                }

                iter++;
                if (iter % 10 == 0) info(".");

                if (PGmax_new - PGmin_new <= eps)
                {
                    if (active_size == l)
                        break;
                    else
                    {
                        active_size = l;
                        info("*");
                        PGmax_old = Double.PositiveInfinity;
                        PGmin_old = Double.NegativeInfinity;
                        continue;
                    }
                }
                PGmax_old = PGmax_new;
                PGmin_old = PGmin_new;
                if (PGmax_old <= 0) PGmax_old = Double.PositiveInfinity;
                if (PGmin_old >= 0) PGmin_old = Double.NegativeInfinity;
            }


            info("\noptimization finished, #iter = {0}", iter);
            if (iter >= max_iter) info("\nWARNING: reaching max number of iterations\nUsing -s 2 may be faster (also see FAQ)\n");


            // calculate objective value

            double v = 0;
            int nSV = 0;
            for (i = 0; i < w_size; i++)
                v += w[i] * w[i];
            for (i = 0; i < l; i++)
            {
                v += alpha[i] * (alpha[i] * diag[GETI(y, i)] - 2);
                if (alpha[i] > 0) ++nSV;
            }
            info("Objective value = {0}", v / 2);
            info("nSV = {0}", nSV);
        }
Exemplo n.º 4
0
 public Parameter(SolverType solverType, double C, double eps, double p ) {
     setSolverType(solverType);
     setC(C);
     setEps(eps);
     setP(p);
 }
Exemplo n.º 5
0
 public Parameter(SolverType solver, double C, double eps ):this(solver, C, eps, 0.1) {
     
 }
Exemplo n.º 6
0
 public void setSolverType(SolverType solverType) {
     if (solverType == null) throw new ArgumentException("solver type must not be null");
     this.solverType = solverType;
 }
Exemplo n.º 7
0
        internal void parse_command_line(string[] argv)
        {
            int i;

            // eps: see setting below
            Parameter = new Parameter(SolverType.getById(SolverType.L2R_L2LOSS_SVC_DUAL), 1, Double.PositiveInfinity, 0.1);
            // default values
            Bias             = -1;
            cross_validation = false;


            // parse options
            for (i = 0; i < argv.Length; i++)
            {
                if (argv[i][0] != '-')
                {
                    break;
                }
                if (++i >= argv.Length)
                {
                    exit_with_help();
                }
                switch (argv[i - 1][1])
                {
                case 's':
                    Parameter.solverType = SolverType.getById(Linear.atoi(argv[i]));
                    break;

                case 'c':
                    Parameter.setC(Linear.atof(argv[i]));
                    break;

                case 'p':
                    Parameter.setP(Linear.atof(argv[i]));
                    break;

                case 'e':
                    Parameter.setEps(Linear.atof(argv[i]));
                    break;

                case 'B':
                    Bias = Linear.atof(argv[i]);
                    break;

                case 'w':
                    int    weightLabel = int.Parse(argv[i - 1].Substring(2));
                    double weight      = double.Parse(argv[i]);
                    Parameter.weightLabel = addToArray(Parameter.weightLabel, weightLabel);
                    Parameter.weight      = addToArray(Parameter.weight, weight);
                    break;

                case 'v':
                    cross_validation = true;
                    nr_fold          = int.Parse(argv[i]);
                    if (nr_fold < 2)
                    {
                        Console.Error.WriteLine("n-fold cross validation: n must >= 2");
                        exit_with_help();
                    }
                    break;

                case 'q':
                    i--;
                    Linear.disableDebugOutput();
                    break;

                default:
                    Console.Error.WriteLine("unknown option");
                    exit_with_help();
                    break;
                }
            }


            // determine filenames


            if (i >= argv.Length)
            {
                exit_with_help();
            }


            inputFilename = argv[i];


            if (i < argv.Length - 1)
            {
                modelFilename = argv[i + 1];
            }
            else
            {
                int p = argv[i].LastIndexOf('/');
                ++p; // whew...
                modelFilename = argv[i].Substring(p) + ".model";
            }


            if (Parameter.eps == Double.PositiveInfinity)
            {
                switch (Parameter.solverType.getId())
                {
                case SolverType.L2R_LR:
                case SolverType.L2R_L2LOSS_SVC:
                    Parameter.setEps(0.01);
                    break;

                case SolverType.L2R_L2LOSS_SVR:
                    Parameter.setEps(0.001);
                    break;

                case SolverType.L2R_L2LOSS_SVC_DUAL:
                case SolverType.L2R_L1LOSS_SVC_DUAL:
                case SolverType.MCSVM_CS:
                case SolverType.L2R_LR_DUAL:
                    Parameter.setEps(0.1);
                    break;

                case SolverType.L1R_L2LOSS_SVC:
                case SolverType.L1R_LR:
                    Parameter.setEps(0.01);
                    break;

                case SolverType.L2R_L1LOSS_SVR_DUAL:
                case SolverType.L2R_L2LOSS_SVR_DUAL:
                    Parameter.setEps(0.1);
                    break;

                default:
                    throw new InvalidOperationException("unknown solver type: " + Parameter.solverType);
                }
            }
        }