docs: public void realForward(float[] a) {
  		if (isPowerOfTwo == false) {
  			throw new IllegalArgumentException("rows and columns must be power of two numbers");
  		} else {
  			for (int r = 0; r < rows; r++) {
  				fftColumns.realForward(a, r * columns);
  			}
  			cdft2d_sub(-1, a, true);
  			rdft2d_sub(1, a);
  		}
  	}