mexnnz.c
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	/***********************************************************************
	* mexnnz.c: get number of non-zero elements of a matrix M
	*
	* nnz = mexnnzt(M);
	*
	* SDPT3: version 3.0
	* Copyright (c) 1997 by
	* K.C. Toh, M.J. Todd, R.H. Tutuncu
	* Last Modified: 2 Feb 01
	***********************************************************************/

	#include <mex.h>
	#include <math.h>

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

	{ double A, nnz;
	mwIndex irA, jcA;

	int NZmax, m, n, isspA, j, k, jm, nnztmp;

	/* CHECK FOR PROPER NUMBER OF ARGUMENTS */

	if (nrhs != 1){
	mexErrMsgTxt("mexnnz: requires 1 input arguments."); }
	else if (nlhs>1){
	mexErrMsgTxt("mexnnz: requires 1 output argument."); }

	/* CHECK THE DIMENSIONS */

	plhs[0] = mxCreateDoubleMatrix(1,1,mxREAL);
	nnz = mxGetPr(plhs[0]);
	if (mxGetPr(prhs[0]) == NULL) {
	nnz[0] = 0.0;
	return;
	}
	m = mxGetM(prhs[0]);
	n = mxGetN(prhs[0]);
	A = mxGetPr(prhs[0]);
	isspA = mxIsSparse(prhs[0]);
	if (isspA) {
	irA = mxGetIr(prhs[0]);
	jcA = mxGetJc(prhs[0]);
	NZmax = jcA[n];
	}
	/*** main body ***/
	nnztmp = 0;
	if (isspA) {
	for (k=0; k<NZmax; k++) {
	if (A[k] != 0) { nnztmp++; }
	}
	} else {
	for (j=0; j<n; j++) {
	jm = j*m;
	for (k=0; k<m; k++) {
	if (A[k+jm] !=0) { nnztmp++; }
	}
	}
	}
	nnz[0] = (double)nnztmp;
	return;
	}
	/**********************************************************/