[ot][spam][crazy][data] transformer model 'attention' improvement

[Undiscussed Horrific Abuse, Victim & Survivor of]

in memory-efficient-attention/attention_torch.py, around line 15,
attn_weights has dimension qhk.  so it's holding the chunked O(n^2)->O(n)
it's biased and masked and maxed, and then turned into exp_weights
which has the same size but different values.
exp_weights is multipled with values to make exp_values, dotting the
value dimenion from values with the key dimension from exp_weights,
with an output of dimension qhf, O(n).

in the original implementaiton, exp_weights and attn_weights are then
discarded, leaving the memory at O(n).

my addition of saving all the exp_weights or attn_weights does indeed
prevent the improvement. whoo! i need to figure out how to retain and
continue to act on my skills and knowledge, pretty badly.