Regional compilation recipe

.jenkins/metadata.json

@@ -58,6 +58,9 @@
   "recipes_source/torch_compile_user_defined_triton_kernel_tutorial.py": {
     "needs": "linux.g5.4xlarge.nvidia.gpu"
   },
+  "recipes_source/regional_compilation.py": {
+    "needs": "linux.g5.4xlarge.nvidia.gpu"
+  },
   "advanced_source/semi_structured_sparse.py": {
     "needs": "linux.g5.4xlarge.nvidia.gpu"
   },

recipes_source/recipes/README.txt

@@ -56,3 +56,7 @@ PyTorch Recipes
 14. amp_recipe.py
          Automatic Mixed Precision
          https://pytorch.org/tutorials/recipes/amp_recipe.html
+
+15. regional_compilation.py
+	Reducing torch.compile cold start compilation time with regional compilation
+         https://pytorch.org/tutorials/recipes/regional_compilation.html

recipes_source/recipes_index.rst

@@ -339,6 +339,15 @@ Recipes are bite-sized, actionable examples of how to use specific PyTorch featu
    :link: ../recipes/torch_compile_caching_tutorial.html
    :tags: Model-Optimization
 
+.. Reducing Cold Start Compilation Time with Regional Compilation
+
+.. customcarditem::
+   :header: Reducing torch.compile cold start compilation time with regional compilation
+   :card_description: Learn how to use regional compilation to control cold start compile time
+   :image: ../_static/img/thumbnails/cropped/generic-pytorch-logo.png
+   :link: ../recipes/regional_compilation.html
+   :tags: Model-Optimization
+
 .. Intel(R) Extension for PyTorch*
 
 .. customcarditem::

recipes_source/regional_compilation.py

@@ -0,0 +1,171 @@
+"""
+Reducing torch.compile cold start compilation time with regional compilation
+============================================================================
+
+**Author:** `Animesh Jain <https://github.com/anijain2305>`_
+As deep learning models get larger, the compilation time of these models also
+increases. This extended compilation time can result in a large startup time in
+inference services or wasted resources in large-scale training. This recipe
+shows an example of how to reduce the cold start compilation time by choosing to
+compile a repeated region of the model instead of the entire model.
+
+Prerequisites
+----------------
+
+* Pytorch 2.5 or later
+Setup
+-----
+Before we begin, we need to install ``torch`` if it is not already
+available.
+
+.. code-block:: sh
+
+   pip install torch
+
+.. note:: 
+   This feature is available starting with the 2.5 release. If you are using version 2.4,
+   you can enable the configuration flag ``torch._dynamo.config.inline_inbuilt_nn_modules=True``
+   to prevent recompilations during regional compilation. In version 2.5, this flag is enabled by default.
+"""
+
+
+
+######################################################################
+# Steps
+# -----
+# 
+# In this recipe, we will follow these steps:
+#
+# 1. Import all necessary libraries.
+# 2. Define and initialize a neural network with repeated regions.
+# 3. Understand the difference between the full model and the regional compilation.
+# 4. Measure the compilation time of the full model and the regional compilation.
+# 
+# First, let's import the necessary libraries for loading our data: 
+# 
+# 
+# 
+
+import torch
+import torch.nn as nn
+from time import perf_counter
+
+##########################################################
+# Next, let's define and initialize a neural network with repeated regions.
+# 
+# Typically, neural networks are composed of repeated layers. For example, a
+# large language model is composed of many Transformer blocks. In this recipe,
+# we will create a ``Layer`` using the ``nn.Module`` class as a proxy for a repeated region.
+# We will then create a ``Model`` which is composed of 64 instances of this
+# ``Layer`` class.
+# 
+class Layer(torch.nn.Module):
+    def __init__(self):
+        super().__init__()
+        self.linear1 = torch.nn.Linear(10, 10)
+        self.relu1 = torch.nn.ReLU()
+        self.linear2 = torch.nn.Linear(10, 10)
+        self.relu2 = torch.nn.ReLU()
+
+    def forward(self, x):
+        a = self.linear1(x)
+        a = self.relu1(a)
+        a = torch.sigmoid(a)
+        b = self.linear2(a)
+        b = self.relu2(b)
+        return b
+
+class Model(torch.nn.Module):
+    def __init__(self, apply_regional_compilation):
+        super().__init__()
+        self.linear = torch.nn.Linear(10, 10)
+        # Apply compile only to the repeated layers.
+        if apply_regional_compilation:
+            self.layers = torch.nn.ModuleList([torch.compile(Layer()) for _ in range(64)])
+        else:
+            self.layers = torch.nn.ModuleList([Layer() for _ in range(64)])
+
+    def forward(self, x):
+        # In regional compilation, the self.linear is outside of the scope of `torch.compile`.
+        x = self.linear(x)
+        for layer in self.layers:
+            x = layer(x)
+        return x
+
+####################################################
+# Next, let's review the difference between the full model and the regional compilation.
+# 
+# In full model compilation, the entire model is compiled as a whole. This is the common approach 
+# most users take with ``torch.compile``. In this example, we apply ``torch.compile`` to
+# the ``Model`` object. This will effectively inline the 64 layers, producing a
+# large graph to compile. You can look at the full graph by running this recipe
+# with ``TORCH_LOGS=graph_code``.
+# 
+#
+
+model = Model(apply_regional_compilation=False).cuda()
+full_compiled_model = torch.compile(model)
+
+
+###################################################
+# The regional compilation, on the other hand, compiles a region of the model.
+# By strategically choosing to compile a repeated region of the model, we can compile a
+# much smaller graph and then reuse the compiled graph for all the regions.
+# In the example, ``torch.compile`` is applied only to the ``layers`` and not the full model.
+# 
+
+regional_compiled_model = Model(apply_regional_compilation=True).cuda()
+
+# Applying compilation to a repeated region, instead of full model, leads to
+# large savings in compile time. Here, we will just compile a layer instance and
+# then reuse it 64 times in the ``Model`` object.
+# 
+# Note that with repeated regions, some part of the model might not be compiled.
+# For example, the ``self.linear`` in the ``Model`` is outside of the scope of
+# regional compilation.
+# 
+# Also, note that there is a tradeoff between performance speedup and compile
+# time. Full model compilation involves a larger graph and,
+# theoretically, offers more scope for optimizations. However, for practical
+# purposes and depending on the model, we have observed many cases with minimal
+# speedup differences between the full model and regional compilation.
+
+
+###################################################
+# Next, let's measure the compilation time of the full model and the regional compilation.
+#
+# ``torch.compile`` is a JIT compiler, which means that it compiles on the first invocation.
+# In the code below, we measure the total time spent in the first invocation. While this method is not 
+# precise, it provides a good estimate since the majority of the time is spent in
+# compilation.
+
+def measure_latency(fn, input):
+    # Reset the compiler caches to ensure no reuse between different runs
+    torch.compiler.reset()
+    with torch._inductor.utils.fresh_inductor_cache():
+        start = perf_counter()
+        fn(input)
+        torch.cuda.synchronize()
+        end = perf_counter()
+        return end - start
+
+input = torch.randn(10, 10, device="cuda")
+full_model_compilation_latency = measure_latency(full_compiled_model, input)
+print(f"Full model compilation time = {full_model_compilation_latency:.2f} seconds")
+
+regional_compilation_latency = measure_latency(regional_compiled_model, input)
+print(f"Regional compilation time = {regional_compilation_latency:.2f} seconds")
+
+############################################################################
+# Conclusion
+# -----------
+#
+# This recipe shows how to control the cold start compilation time if your model
+# has repeated regions. This approach requires user modifications to apply `torch.compile` to
+# the repeated regions instead of more commonly used full model compilation. We
+# are continually working on reducing cold start compilation time.
+# 
+# This feature is available with 2.5 release. If you are on 2.4, you can use a
+# config flag - `torch._dynamo.config.inline_inbuilt_nn_modules=True` to avoid
+# recompilations on the regional compilation. In 2.5, this flag is turned on by
+# default.