that it's too computationally expensive if there's some middle ground that we can have in between so that middle ground is actually just very simple you instead of taking one point and instead taking all of the points let take a mini batch of points so maybe something on the order of 10 20 30 100 maybe depending on how rough or accurate you want that approximation of your gradient to be and how much you want to trade off speed and computational efficiency now the true gradient is just obtained by averaging the gradient from each of