Add ZeRO++ to DeepSpeed usage docs (#2166)

* added zeropp to deepspeed doc file

* minor edit to clarify hpz size

docs/source/usage_guides/deepspeed.md

@@ -15,14 +15,15 @@ rendered properly in your Markdown viewer.
 
 # DeepSpeed 
 
-[DeepSpeed](https://github.com/microsoft/DeepSpeed) implements everything described in the [ZeRO paper](https://arxiv.org/abs/1910.02054). Currently, it provides full support for:
+[DeepSpeed](https://github.com/microsoft/DeepSpeed) implements everything described in the [ZeRO paper](https://arxiv.org/abs/1910.02054). Some of the salient optimizations are:
 
 1. Optimizer state partitioning (ZeRO stage 1)
 2. Gradient partitioning (ZeRO stage 2)
 3. Parameter partitioning (ZeRO stage 3)
 4. Custom mixed precision training handling
 5. A range of fast CUDA-extension-based optimizers
 6. ZeRO-Offload to CPU and Disk/NVMe
+7. Heirarchical partitioning of model parameters (ZeRO++)
 
 ZeRO-Offload has its own dedicated paper: [ZeRO-Offload: Democratizing Billion-Scale Model Training](https://arxiv.org/abs/2101.06840). And NVMe-support is described in the paper [ZeRO-Infinity: Breaking the GPU
 Memory Wall for Extreme Scale Deep Learning](https://arxiv.org/abs/2104.07857).
@@ -44,7 +45,7 @@ won't be possible on a single GPU.
 
 Training:
 
-1. DeepSpeed ZeRO training supports the full ZeRO stages 1, 2 and 3 as well as CPU/Disk offload of optimizer states, gradients and parameters. 
+1. 🤗 Accelerate integrates all features of DeepSpeed ZeRO. This includes all the ZeRO stages 1, 2 and 3 as well as ZeRO-Offload, ZeRO-Infinity (which can offload to disk/NVMe) and ZeRO++.
 Below is a short description of Data Parallelism using ZeRO - Zero Redundancy Optimizer along with diagram from this [blog post](https://www.microsoft.com/en-us/research/blog/zero-deepspeed-new-system-optimizations-enable-training-models-with-over-100-billion-parameters/)
 ![ZeRO Data Parallelism](https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/parallelism-zero.png)
 
@@ -60,6 +61,8 @@ Below is a short description of Data Parallelism using ZeRO - Zero Redundancy Op
 
  e. **Param Offload**: Offloads the model parameters to CPU/Disk building on top of ZERO Stage 3
 
+ f. **Heirarchical Paritioning**: Enables efficient multi-node training with data-parallel training across nodes and ZeRO-3 sharding within a node, built on top of ZeRO Stage 3.
+
 <u>Note</u>: With respect to Disk Offload, the disk should be an NVME for decent speed but it technically works on any Disk
 
 Inference:
@@ -349,6 +352,27 @@ accelerate launch examples/by_feature/deepspeed_with_config_support.py \
 --report_to "wandb"\
 ```
 
+**ZeRO++ Config Example**
+You can use the the features of ZeRO++ by using the appropriate config parameters. Note that ZeRO++ is an extension for ZeRO Stage 3. Here is how the config file can be modified, from [DeepSpeed's ZeRO++ tutorial](https://www.deepspeed.ai/tutorials/zeropp/):
+
+```json
+{
+    "zero_optimization": {
+        "stage": 3,
+        "reduce_bucket_size": "auto",
+
+        "zero_quantized_weights": true,
+        "zero_hpz_partition_size": 8,
+        "zero_quantized_gradients": true,
+
+        "contiguous_gradients": true,
+        "overlap_comm": true
+    }
+}
+```
+
+For heirarchical partitioning, the partition size `zero_hpz_partition_size` should ideally be set to the number of GPUs per node. (For example, the above config file assumes 8 GPUs per node)
+
 **Important code changes when using DeepSpeed Config File**
 
 1. DeepSpeed Optimizers and Schedulers. For more information on these, 
@@ -683,6 +707,8 @@ Papers:
 - [ZeRO: Memory Optimizations Toward Training Trillion Parameter Models](https://arxiv.org/abs/1910.02054)
 - [ZeRO-Offload: Democratizing Billion-Scale Model Training](https://arxiv.org/abs/2101.06840)
 - [ZeRO-Infinity: Breaking the GPU Memory Wall for Extreme Scale Deep Learning](https://arxiv.org/abs/2104.07857)
+- [ZeRO++: Extremely Efficient Collective Communication for Giant Model Training](https://arxiv.org/abs/2306.10209)
+
 
 Finally, please, remember that 🤗 `Accelerate` only integrates DeepSpeed, therefore if you
 have any problems or questions with regards to DeepSpeed usage, please, file an issue with [DeepSpeed GitHub](https://github.com/microsoft/DeepSpeed/issues).