/**
* @param target predicted classes
*/
public static void crossValidation(Problem prob, Parameter param, int nr_fold, double[] target)
{
int i;
int[] fold_start = new int[nr_fold + 1];
int l = prob.l;
int[] perm = new int[l];
for (i = 0; i < l; i++)
perm[i] = i;
for (i = 0; i < l; i++)
{
int j = i + random.Next(l - i);
swap(perm, i, j);
}
for (i = 0; i <= nr_fold; i++)
fold_start[i] = i * l / nr_fold;
for (i = 0; i < nr_fold; i++)
{
int begin = fold_start[i];
int end = fold_start[i + 1];
int j, k;
Problem subprob = new Problem();
subprob.bias = prob.bias;
subprob.n = prob.n;
subprob.l = l - (end - begin);
subprob.x = new Feature[subprob.l][];
subprob.y = new double[subprob.l];
k = 0;
for (j = 0; j < begin; j++)
{
subprob.x[k] = prob.x[perm[j]];
subprob.y[k] = prob.y[perm[j]];
++k;
}
for (j = end; j < l; j++)
{
subprob.x[k] = prob.x[perm[j]];
subprob.y[k] = prob.y[perm[j]];
++k;
}
Model submodel = train(subprob, param);
for (j = begin; j < end; j++)
target[perm[j]] = predict(submodel, prob.x[perm[j]]);
}
}
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);
}
}
}
/**
* A coordinate descent algorithm for
* L1-loss and L2-loss epsilon-SVR dual problem
*
* min_\beta 0.5\beta^T (Q + diag(lambda)) \beta - p \sum_{i=1}^l|\beta_i| + \sum_{i=1}^l yi\beta_i,
* s.t. -upper_bound_i <= \beta_i <= upper_bound_i,
*
* where Qij = xi^T xj and
* D is a diagonal matrix
*
* In L1-SVM case:
* upper_bound_i = C
* lambda_i = 0
* In L2-SVM case:
* upper_bound_i = INF
* lambda_i = 1/(2*C)
*
* Given:
* x, y, p, C
* eps is the stopping tolerance
*
* solution will be put in w
*
* See Algorithm 4 of Ho and Lin, 2012
*/
private static void solve_l2r_l1l2_svr(Problem prob, double[] w, Parameter param)
{
int l = prob.l;
double C = param.C;
double p = param.p;
int w_size = prob.n;
double eps = param.eps;
int i, s, iter = 0;
int max_iter = 1000;
int active_size = l;
int[] index = new int[l];
double d, G, H;
double Gmax_old = Double.PositiveInfinity;
double Gmax_new, Gnorm1_new;
double Gnorm1_init = 0; // initialize to 0 to get rid of Eclipse warning/error
double[] beta = new double[l];
double[] QD = new double[l];
double[] y = prob.y;
// L2R_L2LOSS_SVR_DUAL
double[] lambda = new double[] { 0.5 / C };
double[] upper_bound = new double[] { Double.PositiveInfinity };
if (param.solverType.getId() == SolverType.L2R_L1LOSS_SVR_DUAL)
{
lambda[0] = 0;
upper_bound[0] = C;
}
// Initial beta can be set here. Note that
// -upper_bound <= beta[i] <= upper_bound
for (i = 0; i < l; i++)
beta[i] = 0;
for (i = 0; i < w_size; i++)
w[i] = 0;
for (i = 0; i < l; i++)
{
QD[i] = 0;
foreach (Feature xi in prob.x[i])
{
double val = xi.Value;
QD[i] += val * val;
w[xi.Index - 1] += beta[i] * val;
}
index[i] = i;
}
while (iter < max_iter)
{
Gmax_new = 0;
Gnorm1_new = 0;
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 = -y[i] + lambda[GETI_SVR(i)] * beta[i];
H = QD[i] + lambda[GETI_SVR(i)];
foreach (Feature xi in prob.x[i])
{
int ind = xi.Index - 1;
double val = xi.Value;
G += val * w[ind];
}
double Gp = G + p;
double Gn = G - p;
double violation = 0;
if (beta[i] == 0)
{
if (Gp < 0)
violation = -Gp;
else if (Gn > 0)
violation = Gn;
else if (Gp > Gmax_old && Gn < -Gmax_old)
{
active_size--;
swap(index, s, active_size);
s--;
continue;
}
}
else if (beta[i] >= upper_bound[GETI_SVR(i)])
{
if (Gp > 0)
violation = Gp;
else if (Gp < -Gmax_old)
{
active_size--;
swap(index, s, active_size);
s--;
continue;
}
}
else if (beta[i] <= -upper_bound[GETI_SVR(i)])
{
if (Gn < 0)
violation = -Gn;
else if (Gn > Gmax_old)
{
active_size--;
swap(index, s, active_size);
s--;
continue;
}
}
else if (beta[i] > 0)
violation = Math.Abs(Gp);
else
violation = Math.Abs(Gn);
Gmax_new = Math.Max(Gmax_new, violation);
Gnorm1_new += violation;
// obtain Newton direction d
if (Gp < H * beta[i])
d = -Gp / H;
else if (Gn > H * beta[i])
d = -Gn / H;
else
d = -beta[i];
if (Math.Abs(d) < 1.0e-12) continue;
double beta_old = beta[i];
beta[i] = Math.Min(Math.Max(beta[i] + d, -upper_bound[GETI_SVR(i)]), upper_bound[GETI_SVR(i)]);
d = beta[i] - beta_old;
if (d != 0)
{
foreach (Feature xi in prob.x[i])
{
w[xi.Index - 1] += d * xi.Value;
}
}
}
if (iter == 0) Gnorm1_init = Gnorm1_new;
iter++;
if (iter % 10 == 0) info(".");
if (Gnorm1_new <= eps * Gnorm1_init)
{
if (active_size == l)
break;
else
{
active_size = l;
info("*");
Gmax_old = Double.PositiveInfinity;
continue;
}
}
Gmax_old = Gmax_new;
}
info("noptimization finished, #iter = {0}", iter);
if (iter >= max_iter) info("\nWARNING: reaching max number of iterations\nUsing -s 11 may be faster\n");
// calculate objective value
double v = 0;
int nSV = 0;
for (i = 0; i < w_size; i++)
v += w[i] * w[i];
v = 0.5 * v;
for (i = 0; i < l; i++)
{
v += p * Math.Abs(beta[i]) - y[i] * beta[i] + 0.5 * lambda[GETI_SVR(i)] * beta[i] * beta[i];
if (beta[i] != 0) nSV++;
}
info("Objective value = {0}", v);
info("nSV = {0}", nSV);
}
private static void train_one(Problem prob, Parameter param, double[] w, double Cp, double Cn)
{
double eps = param.eps;
int pos = 0;
for (int i = 0; i < prob.l; i++)
if (prob.y[i] > 0)
{
pos++;
}
int neg = prob.l - pos;
double primal_solver_tol = eps * Math.Max(Math.Min(pos, neg), 1) / prob.l;
IFunction fun_obj = null;
switch (param.solverType.getId())
{
case SolverType.L2R_LR:
{
double[] C = new double[prob.l];
for (int i = 0; i < prob.l; i++)
{
if (prob.y[i] > 0)
C[i] = Cp;
else
C[i] = Cn;
}
fun_obj = new L2R_LrFunction(prob, C);
Tron tron_obj = new Tron(fun_obj, primal_solver_tol);
tron_obj.tron(w);
break;
}
case SolverType.L2R_L2LOSS_SVC:
{
double[] C = new double[prob.l];
for (int i = 0; i < prob.l; i++)
{
if (prob.y[i] > 0)
C[i] = Cp;
else
C[i] = Cn;
}
fun_obj = new L2R_L2_SvcFunction(prob, C);
Tron tron_obj = new Tron(fun_obj, primal_solver_tol);
tron_obj.tron(w);
break;
}
case SolverType.L2R_L2LOSS_SVC_DUAL:
solve_l2r_l1l2_svc(prob, w, eps, Cp, Cn, SolverType.getById(SolverType.L2R_L2LOSS_SVC_DUAL));
break;
case SolverType.L2R_L1LOSS_SVC_DUAL:
solve_l2r_l1l2_svc(prob, w, eps, Cp, Cn, SolverType.getById(SolverType.L2R_L1LOSS_SVC_DUAL));
break;
case SolverType.L1R_L2LOSS_SVC:
{
Problem prob_col = transpose(prob);
solve_l1r_l2_svc(prob_col, w, primal_solver_tol, Cp, Cn);
break;
}
case SolverType.L1R_LR:
{
Problem prob_col = transpose(prob);
solve_l1r_lr(prob_col, w, primal_solver_tol, Cp, Cn);
break;
}
case SolverType.L2R_LR_DUAL:
solve_l2r_lr_dual(prob, w, eps, Cp, Cn);
break;
case SolverType.L2R_L2LOSS_SVR:
{
double[] C = new double[prob.l];
for (int i = 0; i < prob.l; i++)
C[i] = param.C;
fun_obj = new L2R_L2_SvrFunction(prob, C, param.p);
Tron tron_obj = new Tron(fun_obj, param.eps);
tron_obj.tron(w);
break;
}
case SolverType.L2R_L1LOSS_SVR_DUAL:
case SolverType.L2R_L2LOSS_SVR_DUAL:
solve_l2r_l1l2_svr(prob, w, param);
break;
default:
throw new InvalidOperationException("unknown solver type: " + param.solverType);
}
}
/**
* @throws IllegalArgumentException if the feature nodes of prob are not sorted in ascending order
*/
public static Model train(Problem prob, Parameter param)
{
if (prob == null) throw new ArgumentNullException("problem must not be null");
if (param == null) throw new ArgumentNullException("parameter must not be null");
if (prob.n == 0) throw new ArgumentNullException("problem has zero features");
if (prob.l == 0) throw new ArgumentNullException("problem has zero instances");
foreach (Feature[] nodes in prob.x)
{
int indexBefore = 0;
foreach (Feature n_ in nodes)
{
if (n_.Index <= indexBefore)
{
throw new ArgumentException("feature nodes must be sorted by index in ascending order");
}
indexBefore = n_.Index;
}
}
int l = prob.l;
int n = prob.n;
int w_size = prob.n;
Model model = new Model();
if (prob.bias >= 0)
model.nr_feature = n - 1;
else
model.nr_feature = n;
model.solverType = param.solverType;
model.bias = prob.bias;
if (param.solverType.getId() == SolverType.L2R_L2LOSS_SVR || //
param.solverType.getId() == SolverType.L2R_L1LOSS_SVR_DUAL || //
param.solverType.getId() == SolverType.L2R_L2LOSS_SVR_DUAL)
{
model.w = new double[w_size];
model.nr_class = 2;
model.label = null;
checkProblemSize(n, model.nr_class);
train_one(prob, param, model.w, 0, 0);
}
else
{
int[] perm = new int[l];
// group training data of the same class
GroupClassesReturn rv = groupClasses(prob, perm);
int nr_class = rv.nr_class;
int[] label = rv.label;
int[] start = rv.start;
int[] count = rv.count;
checkProblemSize(n, nr_class);
model.nr_class = nr_class;
model.label = new int[nr_class];
for (int i = 0; i < nr_class; i++)
model.label[i] = label[i];
// calculate weighted C
double[] weighted_C = new double[nr_class];
for (int i = 0; i < nr_class; i++)
weighted_C[i] = param.C;
for (int i = 0; i < param.getNumWeights(); i++)
{
int j;
for (j = 0; j < nr_class; j++)
if (param.weightLabel[i] == label[j]) break;
if (j == nr_class) throw new ArgumentException("class label " + param.weightLabel[i] + " specified in weight is not found");
weighted_C[j] *= param.weight[i];
}
// constructing the subproblem
Feature[][] x = new Feature[l][];
for (int i = 0; i < l; i++)
x[i] = prob.x[perm[i]];
Problem sub_prob = new Problem();
sub_prob.l = l;
sub_prob.n = n;
sub_prob.x = new Feature[sub_prob.l][];
sub_prob.y = new double[sub_prob.l];
for (int k = 0; k < sub_prob.l; k++)
sub_prob.x[k] = x[k];
// multi-class svm by Crammer and Singer
if (param.solverType.getId() == SolverType.MCSVM_CS)
{
model.w = new double[n * nr_class];
for (int i = 0; i < nr_class; i++)
{
for (int j = start[i]; j < start[i] + count[i]; j++)
{
sub_prob.y[j] = i;
}
}
SolverMCSVM_CS solver = new SolverMCSVM_CS(sub_prob, nr_class, weighted_C, param.eps);
solver.solve(model.w);
}
else
{
if (nr_class == 2)
{
model.w = new double[w_size];
int e0 = start[0] + count[0];
int k = 0;
for (; k < e0; k++)
sub_prob.y[k] = +1;
for (; k < sub_prob.l; k++)
sub_prob.y[k] = -1;
train_one(sub_prob, param, model.w, weighted_C[0], weighted_C[1]);
}
else
{
model.w = new double[w_size * nr_class];
double[] w = new double[w_size];
for (int i = 0; i < nr_class; i++)
{
int si = start[i];
int ei = si + count[i];
int k = 0;
for (; k < si; k++)
sub_prob.y[k] = -1;
for (; k < ei; k++)
sub_prob.y[k] = +1;
for (; k < sub_prob.l; k++)
sub_prob.y[k] = -1;
train_one(sub_prob, param, w, weighted_C[i], param.C);
for (int j = 0; j < n; j++)
model.w[j * nr_class + i] = w[j];
}
}
}
}
return model;
}
