String dumpArray(String msg, float[][] A, int x1, int x2, int y1, int y2) {
		String s = "dumpArray: " + msg + "\n";
		for (int x = x1; x <= x2; x++)
			s += "\t*" + x + "*";
		for (int y = y2; y >= y1; y--) {
			s += "\n*" + y + "*";
			for (int x = x1; x <= x2; x++)
				s += "\t" + (x < A.length && y < A[x].length ? A[x][y] : Float.NaN);
		}
		return s;
	}