**HIP is a C++ Runtime API and Kernel Language that allows developers to create portable applications for AMD and NVIDIA GPUs from single source code.**
New projects can be developed directly in the portable HIP C++ language and can run on either NVIDIA or AMD platforms. Additionally, HIP provides porting tools which make it easy to port existing CUDA codes to the HIP layer, with no loss of performance as compared to the original CUDA application. HIP is not intended to be a drop-in replacement for CUDA, and developers should expect to do some manual coding and performance tuning work to complete the port.
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* Main branch: This is the stable branch. It is up to date with the latest release branch, for example, if the latest HIP release is rocm-3.9, main branch will be the repository based on this release.
* Release branches. These are branches corresponding to each ROCM release, listed with release tags, such as rocm-3.8, rocm-3.9, etc.
The HIP kernel language defines builtins for determining grid and block coordinates, math functions, short vectors,
atomics, and timer functions.
It also specifies additional defines and keywords for function types, address spaces, and optimization controls (See the [HIP Kernel Language](docs/markdown/hip_kernel_language.md) for a full description).
Here's an example of defining a simple 'vector_square' kernel.
The HIP Runtime API code and compute kernel definition can exist in the same source file - HIP takes care of generating host and device code appropriately.
- On the NVIDIA CUDA platform, HIP provides header file which translate from the HIP runtime APIs to CUDA runtime APIs. The header file contains mostly inlined
- On the AMD ROCm platform, HIP provides a header and runtime library built on top of HIP-Clang compiler. The HIP runtime implements HIP streams, events, and memory APIs,
Thus HIP source code can be compiled to run on either platform. Platform-specific features can be isolated to a specific platform using conditional compilation. Thus HIP
provides source portability to either platform. HIP provides the _hipcc_ compiler driver which will call the appropriate toolchain depending on the desired platform.
* A sample and [blog](http://gpuopen.com/hip-to-be-squared-an-introductory-hip-tutorial) that uses any of [HIPIFY](https://github.com/ROCm-Developer-Tools/HIPIFY/blob/master/README.md) tools to convert a simple app from CUDA to HIP:
The GitHub repository [HIP-Examples](https://github.com/ROCm-Developer-Tools/HIP-Examples.git) contains a hipified version of the popular Rodinia benchmark suite.
The README with the procedures and tips the team used during this porting effort is here: [Rodinia Porting Guide](https://github.com/ROCm-Developer-Tools/HIP-Examples/blob/master/rodinia_3.0/hip/README.hip_porting)
* **hip_runtime_api.h** : Defines HIP runtime APIs and can be compiled with many standard Linux compilers (GCC, ICC, CLANG, etc), in either C or C++ mode.
* **hip_runtime.h** : Includes everything in hip_runtime_api.h PLUS hipLaunchKernel and syntax for writing device kernels and device functions. hip_runtime.h can be compiled using a standard C++ compiler but will expose a subset of the available functions.
* **hipcc** : Compiler driver that can be used to replace nvcc in existing CUDA code. hipcc will call nvcc or HIP-Clang depending on platform and include appropriate platform-specific headers and libraries.
* **hipexamine-perl.sh** : Script to scan the directory, find all code, and report statistics on how much can be ported with HIP (and identify likely features not yet supported).
* **hipconvertinplace-perl.sh** : Script to scan the directory, find all code, and convert the found CUDA code to HIP reporting all unconverted things.
