> **Note:** The published documentation is available at [RCCL](https://rocm.docs.amd.com/projects/rccl/en/latest/index.html) in an organized easy-to-read format that includes a table of contents and search functionality. The documentation source files reside in the [rccl/docs](https://github.com/ROCm/rccl/tree/develop/docs) folder in this repository. As with all ROCm projects, the documentation is open source. For more information, see [Contribute to ROCm documentation](https://rocm.docs.amd.com/en/latest/contribute/contributing.html).
RCCL (pronounced "Rickle") is a stand-alone library of standard collective communication routines for GPUs, implementing all-reduce, all-gather, reduce, broadcast, reduce-scatter, gather, scatter, and all-to-all. There is also initial support for direct GPU-to-GPU send and receive operations. It has been optimized to achieve high bandwidth on platforms using PCIe, xGMI as well as networking using InfiniBand Verbs or TCP/IP sockets. RCCL supports an arbitrary number of GPUs installed in a single node or multiple nodes, and can be used in either single- or multi-process (e.g., MPI) applications.
The collective operations are implemented using ring and tree algorithms and have been optimized for throughput and latency. For best performance, small operations can be either batched into larger operations or aggregated through the API.
The root of this repository has a helper script `install.sh` to build and install RCCL with a single command. It hard-codes configurations that can be specified through invoking cmake directly, but it's a great way to get started quickly and can serve as an example of how to build/install RCCL.
### To build the library using the install script:
--amdgpu_targets Only compile for specified GPU architecture(s). For multiple targets, separate by ';'(builds for all supported GPU architectures by default)
By default, RCCL builds for all GPU targets defined in `DEFAULT_GPUS` in `CMakeLists.txt`. To target specific GPU(s), and potentially reduce build time, use `--amdgpu_targets` as a `;` separated string listing GPU(s) to target.
RCCL package install requires sudo/root access because it installs under `/opt/rocm/`. This is an optional step as RCCL can instead be used directly by including the path containing `librccl.so`.
There are rccl unit tests implemented with the Googletest framework in RCCL. The rccl unit tests require Googletest 1.10 or higher to build and execute properly (installed with the -d option to install.sh).
To invoke the rccl unit tests, go to the build folder, then the test subfolder, and execute the appropriate rccl unit test executable(s).
will run only AllReduce correctness tests with float16 datatype. A list of available filtering environment variables appears at the top of every run. See "Running a Subset of the Tests" at https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests for more information on how to form more advanced filters.
