#include "mex.h"

#include <stdio.h>

#include <math.h>

#include <string.h>

#include "altra.h"

/*

 * -------------------------------------------------------------------

 *                       Function and parameter

 * -------------------------------------------------------------------

 *

 * altra solves the following problem

 *

 * 1/2 \|x-v\|^2 + \sum \lambda_i \|x_{G_i}\|,

 *

 * where x and v are of dimension n,

 *       \lambda_i >=0, and G_i's follow the tree structure

 *

 * The file is implemented in the following in Matlab:

 *

 * x=altra(v, n, ind, nodes);

 *

 * ind is a 3 x nodes matrix.

 *       Each column corresponds to a node.

 *

 *       The first element of each column is the starting index,

 *       the second element of each column is the ending index

 *       the third element of each column corrreponds to \lambbda_i.

 *

 * -------------------------------------------------------------------

 *                       Notices:

 * -------------------------------------------------------------------

 *

 * 1. The nodes in the parameter "ind" should be given in the 

 *    either

 *           the postordering of depth-first traversal

 *    or 

 *           the reverse breadth-first traversal.

 *

 * 2. When each elements of x are penalized via the same L1 

 *    (equivalent to the L2 norm) parameter, one can simplify the input

 *    by specifying 

 *           the "first" column of ind as (-1, -1, lambda)

 *

 *    In this case, we treat it as a single "super" node. Thus in the value

 *    nodes, we only count it once.

 *

 * 3. The values in "ind" are in [1,n].

 *

 * 4. The third element of each column should be positive. The program does

 *    not check the validity of the parameter. 

 *

 *    It is still valid to use the zero regularization parameter.

 *    In this case, the program does not change the values of 

 *    correponding indices.

 *    

 *

 * -------------------------------------------------------------------

 *                       History:

 * -------------------------------------------------------------------

 *

 * Composed by Jun Liu on April 20, 2010

 *

 * For any question or suggestion, please email j.liu@asu.edu.

 *

 */

void mexFunction (int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]){

    double*     v       =   mxGetPr(prhs[0]);

    int         n       =   (int) mxGetScalar(prhs[1]);

    double*     ind     =   mxGetPr(prhs[2]);

    int         nodes   =   (int) mxGetScalar(prhs[3]);

    int i;

    double *x;    

    /* set up output arguments */

    plhs[0] = mxCreateDoubleMatrix(n,1,mxREAL);

    x = mxGetPr(plhs[0]);

    altra(x, v, n, ind, nodes);

}