The Gaussian Difference example resides in the L3/examples/gaussiandifference
directory.
This benchmark tests the performance of the gaussiandifference function. The Difference of Gaussian Filter function can be implemented by applying the Gaussian Filter on the original source image, and that Gaussian blurred image is duplicated as two images. The Gaussian blur function is applied to one of the duplicated images, whereas the other one is stored as it is. Later, perform the Subtraction function on, two times Gaussian applied image and one of the duplicated image.
The tutorial provides a step-by-step guide that covers commands for building and running a kernel.