oneAPI Collective Communications Library documentation (C API)

Note

This document describes the new C API that closely follows the NVIDIA Collective Communications Library (NCCL)* API standard. Documentation for the legacy C++ API can be found here.

About

• Introduction

Get Started

• Getting Started with oneCCL
  • Introduction
  • Installation
    • Linux build
  • Usage
    • Launching Example Application
• Example oneCCL app
  • Prerequisites
  • 1. Include Required Headers
  • 2. Initialize MPI and oneCCL
  • 3. Create and Share Unique ID
  • 4. Associate GPU Device
  • 5. Initialize Communicator
  • 6. Allocate Buffers and Prepare Data
  • 7. Perform a Collective Operation
  • 8. Post-Processing
  • 9. Cleanup
  • Complete code
  • Build and run
• New features of oneCCL with C API
  • Available Plugins
  • How Plugin Selection Works
• How to upgrade from C++ API
  • How to compile using oneCCL C API
  • Key differences between the two APIs

Developer Reference

• API Documentation
  • Communicator Creation API
    • onecclGetVersion()
    • onecclGetUniqueId()
    • onecclExtractVersionComponents()
    • onecclCommInitRank()
    • onecclCommInitRankConfig()
    • onecclCommInitAll()
    • onecclCommFinalize()
    • onecclCommDestroy()
    • onecclCommAbort()
    • onecclCommSplit()
    • onecclGetErrorString()
    • onecclGetLastError()
    • onecclCommCount()
    • onecclCommDevice()
    • onecclCommUserRank()
    • onecclSetDevice()
    • onecclCommGetAsyncError()
  • Collective Functions API
    • onecclReduce()
    • onecclAllReduce()
    • onecclBroadcast()
    • onecclReduceScatter()
    • onecclAllGather()
    • onecclAllToAll()
    • onecclSend()
    • onecclRecv()
    • onecclGroupStart()
    • onecclGroupEnd()
    • onecclRedOpCreatePreMulSum()
    • onecclRedOpDestroy()
  • Types API
    • onecclResult_t
    • onecclDataType_t
    • onecclRedOp_t
    • onecclScalarResidence_t
    • onecclPluginType_t
    • onecclUniqueId
    • onecclConfig
• Environment Variables
  • General
    • CCL_PLUGIN