Perform weight re-init for embedding table in sparse_lookup.py (#22348)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/22348
This is the last step of LRU hash eviction weight re-init. This diff checks if there's evicted values in sparse_lookup, if so call op created in D15709866 to re-init the values for indicies in evicted_values. Also created gradient op for the operator. The gradient op just passes the output gradient as input gradient.
Reviewed By: itomatik
Differential Revision: D16044736
fbshipit-source-id: 9afb85209b0de1038c5153bcb7dfc5f52e0b2abb
