Skip to content
GitLab
Projects Groups Snippets
  • /
  • Help
    • Help
    • Support
    • Community forum
    • Submit feedback
    • Contribute to GitLab
  • Sign in
  • S starpu
  • Project information
    • Project information
    • Activity
    • Labels
    • Members
  • Repository
    • Repository
    • Files
    • Commits
    • Branches
    • Tags
    • Contributors
    • Graph
    • Compare
  • Issues 9
    • Issues 9
    • List
    • Boards
    • Service Desk
    • Milestones
  • Merge requests 5
    • Merge requests 5
  • CI/CD
    • CI/CD
    • Pipelines
    • Jobs
    • Schedules
  • Deployments
    • Deployments
    • Environments
    • Releases
  • Monitor
    • Monitor
    • Incidents
  • Analytics
    • Analytics
    • Value stream
    • CI/CD
    • Repository
  • Snippets
    • Snippets
  • Activity
  • Graph
  • Create a new issue
  • Jobs
  • Commits
  • Issue Boards
Collapse sidebar
  • starpu
  • starpu
  • Merge requests
  • !68

mpi all_reduce

  • Review changes

  • Download
  • Email patches
  • Plain diff
Open Antoine Jego requested to merge all_redux into replicated_tasks Oct 20, 2022
  • Overview 11
  • Commits 23
  • Pipelines 15
  • Changes 11

This MR targets replicated_tasks as it can be tied with the use of alternative_source.

StarPU lacks an all-reduce. While this operation could be done with a reduce then a broadcast, it might be interesting to have a shorter operation.

This MR proposes something simple akin to the butterfly pattern in an FFT. It works with non-power-of-2 contributions by adding an extra step. If we look at the litterature for MPI collectives in the 00s, a lot of patterns for all-reduce exists, sometimes involving halving the results (it makes sense with matrices, and could be achieved with partitioning in StarPU). A trade-off exists between latency and bandwidth.

The present implementation should be latency optimal (i.e. there are fewer steps than reduce + bcast).

  • docs
  • example
    • "simple" all-reduce, providing a benchmark
    • all-reduce + alternative_source ?
  • fortran interface
Edited Oct 20, 2022 by Antoine Jego
Assignee
Assign to
Reviewers
Request review from
Time tracking
Source branch: all_redux