support for true batches with multipack (#1230)

* support for true batches with multipack

* patch the map dataset fetcher to handle batches with packed indexes

* patch 4d mask creation for sdp attention

* better handling for BetterTransformer

* patch general case for 4d mask

* setup forward patch. WIP

* fix patch file

* support for multipack w/o flash attention for llama

* cleanup

* add warning about bf16 vs fp16 for multipack with sdpa

* bugfixes

* add 4d multipack tests, refactor patches

* update tests and add warnings

* fix e2e file check

* skip sdpa test if not at least torch 2.1.1, update docs

README.md

@@ -37,6 +37,9 @@ Features:
   - [Inference](#inference)
   - [Merge LORA to Base](#merge-lora-to-base)
   - [Special Tokens](#special-tokens)
+- Advanced Topics
+  - [Multipack](./docs/multipack.md)<svg width="24" height="24" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path d="M17 13.5v6H5v-12h6m3-3h6v6m0-6-9 9" class="icon_svg-stroke" stroke="#666" stroke-width="1.5" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg>
+  - [RLHF & DPO](./docs/rlhf.md)<svg width="24" height="24" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><path d="M17 13.5v6H5v-12h6m3-3h6v6m0-6-9 9" class="icon_svg-stroke" stroke="#666" stroke-width="1.5" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg>
 - [Common Errors](#common-errors-)
   - [Tokenization Mismatch b/w Training & Inference](#tokenization-mismatch-bw-inference--training)
 - [Debugging Axolotl](#debugging-axolotl)