HIP (Heterogeneous-compute Interface for Portability) is a C++ header file and library designed by AMD to provide a portable programming interface for heterogeneous computing systems, specifically targeting both AMD and NVIDIA GPUs. It aims to minimize code changes required when migrating applications between AMD’s ROCm platform and NVIDIA’s CUDA platform. Essentially, HIP allows developers to write code once and, with minimal modifications, run it on either AMD or NVIDIA GPUs, fostering broader hardware compatibility and reducing vendor lock-in.

The core philosophy of HIP revolves around a source-to-source translation tool, `hipcc`, which converts HIP code into equivalent CUDA code. This means developers primarily write in HIP C++, a language very similar to CUDA C++, leveraging familiar programming constructs. `hipcc` then handles the complexities of translating these constructs into the specific instructions required by the target GPU architecture. This approach differs from runtime dispatching or abstraction layers, as it focuses on static compilation and optimization for the target hardware. The repository contains the HIP runtime, compiler infrastructure, and a suite of examples demonstrating its usage.

The repository’s structure reflects its role as a compiler and runtime environment. Key components include the `hip` directory containing the core HIP headers and runtime library, `tools` which houses `hipcc` and other utility tools, `examples` providing practical demonstrations of HIP features, and `test` containing comprehensive tests to ensure functionality and correctness. The `include` directory contains the necessary header files for HIP programming, while the `lib` directory holds the compiled runtime libraries. The build system utilizes CMake, making it relatively straightforward to build HIP on various platforms.

HIP supports a wide range of CUDA C++ features, including kernels, shared memory, synchronization primitives (like barriers and atomics), and memory management. However, it’s not a 1:1 mapping. Some CUDA features may not have direct HIP equivalents, requiring developers to use alternative approaches or conditional compilation. The HIP documentation provides detailed guidance on these differences and recommended workarounds. A significant effort is dedicated to maintaining compatibility with newer CUDA versions, ensuring that HIP can leverage advancements in CUDA while remaining portable.

Beyond the core HIP language and compiler, the repository also includes support for various extensions and integrations. This includes support for ROCm’s features like HIP-level memory management and profiling tools. Furthermore, HIP is increasingly integrated with popular machine learning frameworks like TensorFlow and PyTorch, allowing developers to accelerate their models on AMD GPUs with minimal code changes. The project is actively maintained by AMD and the open-source community, with regular updates and improvements focused on performance, compatibility, and feature enhancements. The goal is to establish HIP as a standard for portable heterogeneous programming, enabling developers to unlock the full potential of diverse GPU architectures.