Patched docs for torch_compile_tutorial (#2936)

* Patched docs for torch_compile_tutorial

---------

Co-authored-by: Svetlana Karslioglu <svekars@meta.com>

Author: ignaciobartol

intermediate_source/torch_compile_tutorial.py

@@ -73,17 +73,21 @@ def foo(x, y):
 
 ######################################################################
 # Alternatively, we can decorate the function.
+t1 = torch.randn(10, 10)
+t2 = torch.randn(10, 10)
 
 @torch.compile
 def opt_foo2(x, y):
     a = torch.sin(x)
     b = torch.cos(y)
     return a + b
-print(opt_foo2(torch.randn(10, 10), torch.randn(10, 10)))
+print(opt_foo2(t1, t2))
 
 ######################################################################
 # We can also optimize ``torch.nn.Module`` instances.
 
+t = torch.randn(10, 100)
+
 class MyModule(torch.nn.Module):
     def __init__(self):
         super().__init__()
@@ -94,7 +98,101 @@ def forward(self, x):
 
 mod = MyModule()
 opt_mod = torch.compile(mod)
-print(opt_mod(torch.randn(10, 100)))
+print(opt_mod(t))
+
+######################################################################
+# torch.compile and Nested Calls
+# ------------------------------
+# Nested function calls within the decorated function will also be compiled.
+
+def nested_function(x):
+    return torch.sin(x)
+
+@torch.compile
+def outer_function(x, y):
+    a = nested_function(x)
+    b = torch.cos(y)
+    return a + b
+
+print(outer_function(t1, t2))
+
+######################################################################
+# In the same fashion, when compiling a module all sub-modules and methods
+# within it, that are not in a skip list, are also compiled.
+
+class OuterModule(torch.nn.Module):
+    def __init__(self):
+        super().__init__()
+        self.inner_module = MyModule()
+        self.outer_lin = torch.nn.Linear(10, 2)
+
+    def forward(self, x):
+        x = self.inner_module(x)
+        return torch.nn.functional.relu(self.outer_lin(x))
+
+outer_mod = OuterModule()
+opt_outer_mod = torch.compile(outer_mod)
+print(opt_outer_mod(t))
+
+######################################################################
+# We can also disable some functions from being compiled by using
+# ``torch.compiler.disable``. Suppose you want to disable the tracing on just
+# the ``complex_function`` function, but want to continue the tracing back in
+# ``complex_conjugate``. In this case, you can use
+# ``torch.compiler.disable(recursive=False)`` option. Otherwise, the default is
+# ``recursive=True``.
+
+def complex_conjugate(z):
+    return torch.conj(z)
+
+@torch.compiler.disable(recursive=False)
+def complex_function(real, imag):
+    # Assuming this function cause problems in the compilation
+    z = torch.complex(real, imag)
+    return complex_conjugate(z)
+
+def outer_function():
+    real = torch.tensor([2, 3], dtype=torch.float32)
+    imag = torch.tensor([4, 5], dtype=torch.float32)
+    z = complex_function(real, imag)
+    return torch.abs(z)
+
+# Try to compile the outer_function
+try:
+    opt_outer_function = torch.compile(outer_function)
+    print(opt_outer_function())
+except Exception as e:
+    print("Compilation of outer_function failed:", e)
+
+######################################################################
+# Best Practices and Recommendations
+# ----------------------------------
+#
+# Behavior of ``torch.compile`` with Nested Modules and Function Calls
+#
+# When you use ``torch.compile``, the compiler will try to recursively compile
+# every function call inside the target function or module inside the target
+# function or module that is not in a skip list (such as built-ins, some functions in
+# the torch.* namespace).
+# 
+# **Best Practices:**
+#
+# 1. **Top-Level Compilation:** One approach is to compile at the highest level
+# possible (i.e., when the top-level module is initialized/called) and
+# selectively disable compilation when encountering excessive graph breaks or
+# errors. If there are still many compile issues, compile individual
+# subcomponents instead.
+#
+# 2. **Modular Testing:** Test individual functions and modules with ``torch.compile``
+# before integrating them into larger models to isolate potential issues.
+#
+# 3. **Disable Compilation Selectively:** If certain functions or sub-modules
+# cannot be handled by `torch.compile`, use the `torch.compiler.disable` context
+# managers to recursively exclude them from compilation.
+#
+# 4. **Compile Leaf Functions First:** In complex models with multiple nested
+# functions and modules, start by compiling the leaf functions or modules first.
+# For more information see `TorchDynamo APIs for fine-grained tracing <https://pytorch.org/docs/stable/torch.compiler_fine_grain_apis.html>`__.
 
 ######################################################################
 # Demonstrating Speedups