docs: public void realInverse(double[] a, boolean scale) {
  		// handle special case
  		if( rows == 1 || columns == 1 ) {
  			if( rows > 1 )
  				fftRows.realInverse(a, scale);
  			else
  				fftColumns.realInverse(a, scale);
  			return;
  		}
  
  		if (isPowerOfTwo == false) {
  			throw new IllegalArgumentException("rows and columns must be power of two numbers");
  		} else {
  			rdft2d_sub(-1, a);
  			cdft2d_sub(1, a, scale);
  			for (int r = 0; r < rows; r++) {
  				fftColumns.realInverse(a, r * columns, scale);
  			}
  		}
  	}