Describe the bug
By design, in each training epoch, SmartCacheDataset only presents cache_num of data points to the data loader where data shuffling is achieved.

There's a potential of insufficient shuffling at the initial training epoches, when cache_num/cache_rate is small, and the cache replacements are not fast enough.

Expected behavior
would be great to have a global data list shuffling before running the training epochs with the cached subsets.

Additional context