keras predict_generator is shuffling its output when using a keras.utils.Sequence

Question

I am using keras to build a model that inputs 720x1280 images and outputs a value.

I am having a problem with keras.models.Sequential.predict_generator

Answer 1

predict_generator was not shuffling my predictions, after all. The problem was with the __getitem__ method. For instance, usingn_batch=32, the method would yield values from 1 to 32, then from 2 to 33 and so forth, instead of from 1 to 32, 33 to 64, etc.

Changing the method as follows solves the problem

 def __getitem__(self, idx):
    # batch_x is a numpy.ndarray
    idx_min = idx*self.batch_size
    idx_max = min(idx_min + self.batch_size, self.n)
    batch_x = (
            self.images[idx_min:idx_max]
            .concatenate()
            .reshape(self.batch_size, 720, 1280, 1)
            ) 
    batch_y = self.hf[idx_min:idx_max]