import Jama.Matrix;


public class MathUtils {
	final static double lfEps = 0.00000000001;
	
	public static void arrSubtrAndStore(double [] arrLfSubFrom,
			double [] arrLfSub) {
		for(int i = 0; i < arrLfSub.length; ++i) {
			arrLfSubFrom[i] -= arrLfSub[i];
		}
	}

	public static void linCombine(double lfA, double [] arrLfA,
			double lfB, double [] arrLfB, double [] arrLfStore) {
		for(int i = 0; i < arrLfStore.length; ++i) {
			arrLfStore[i] = lfA*arrLfA[i] + lfB * arrLfB[i];
		}
	}
	
	public static double [] arrDblCpy(double [] arrLfSrc, int nLen) {
		double [] arrLfRslt = new double[nLen];
		for(int i = 0; i < nLen; ++i) {
			arrLfRslt[i] = arrLfSrc[i];
		}
		return arrLfRslt;
	}
	
	public static double [] arrDblCpyRange(double [] arrLfSrc, int nStart, int nStop) {
		int nLen = nStop-nStart;
		double [] arrLfRslt = new double[nLen];
		for(int i = 0; i < nLen; ++i) {
			arrLfRslt[i] = arrLfSrc[i+nStart];
		}
		return arrLfRslt;
	}
	
	public static String arrToString(double [] arrLfPt) {
		String strRslt = "(";
		for(int i = 0; i < arrLfPt.length; ++i) {
			strRslt = strRslt + (new Double(arrLfPt[i])).toString();
			if(i < arrLfPt.length-1) {
				strRslt += ",";
			}
		}
		strRslt += ")";
		return strRslt;
	}
	
	public static double arrDiffDot(double [] arrLf1, double [] arrLf2,
			double [] arrLfDot) {
		double lfResult = 0.0;
		for(int i = 0; i < arrLf1.length; ++i) {
			double lfTmp = arrLf1[i] - arrLf2[i];
			lfResult += lfTmp*arrLfDot[i];
		}
		return lfResult;
	}
	
	public static double arrDot(double [] arrLf1, double [] arrLf2) {
		double lfResult = 0.0;
		for(int i = 0; i < arrLf1.length; ++i) {
			lfResult += arrLf1[i]*arrLf2[i];
		}
		return lfResult;
	}

	public static double arrDistSqrd(double [] arrLf1, double [] arrLf2) {
		double lfResult = 0.0;
		for(int i = 0; i < arrLf1.length; ++i) {
			double lfTmp = arrLf1[i] - arrLf2[i];
			lfResult += lfTmp*lfTmp;
		}
		return lfResult;
	}
	
	public static void arrMults(double [] arrLfMult, double lfMultBy) {
		for(int i = 0; i < arrLfMult.length; ++i) {
			arrLfMult[i] *= lfMultBy;
		}
	}
	
	public static void arrCpy(double [] arrLfSrc, double [] arrLfDst) {
		for(int i = 0; i < arrLfSrc.length; ++i) {
			arrLfDst[i] = arrLfSrc[i];
		}
	}
	
	public static void normalize(double [] arrLfToNorm) {
		double lfNorm = arrDot(arrLfToNorm, arrLfToNorm);
		if(lfNorm < lfEps*lfEps) {
			return;
		}
		lfNorm = 1.0/Math.sqrt(lfNorm);
		arrMults(arrLfToNorm, lfNorm);
	}
	
	
	/**
     * Helper function to force a matrix to be symmetric in the simplest possible way
     * (just copy (i,j) onto (j,i).
     * Only useful for matrices that are almost symmetric, except for numerical error
     * @param M
     */
    static public void makeSymmetric(Matrix M) {
    	for(int i = 0; i < M.getRowDimension(); ++i) {
    		for(int j = i+1; j < M.getColumnDimension(); ++j) {
    			M.set(j, i, 0.5*(M.get(j,i) + M.get(i, j)));
    			M.set(i, j, M.get(j, i));
    		}
    	}
    }
}