Skip to main content

C++ Extension for Elementwise Add

When Python is too slow, drop into C++ — and PyTorch will still treat it like a built-in op.

Key Insight​

A C++ extension lets you write an operation in C++ (or CUDA), compile it, and call it from Python as if it were built in. Writing an elementwise add_cuda, registering it, and calling it shows the full path a call travels — from Python, through the dispatcher, down to a compiled kernel.

Why This Matters​

This is your escape hatch when an operation is missing or too slow. A custom extension is exactly how new ops enter PyTorch, so walking the path once makes the framework feel less like a black box.