OpenMP - AshokBhat/notes GitHub Wiki

About

• Open Multi-Processing API

FAQ

• What is OpenMP?
  • Stands for Open Multi-Processing
  • An API
• What is the use?
  • Write parallel programs for shared memory use-case
  • Parallel programming within a SoC
• What does it consist of?
  • Compiler directives
  • Library routines
  • Environment variables
• Which languages are supported?
  • C, C++ and FORTRAN
• Who should support OpenMP for a program to use it?
  • A compiler should support OpenMP
• Who drives it?
  • OpenMP Architecture Review Board 
  • A nonprofit technology consortium 

Major versions

OpenMP 3.0

• When was it released?
  • 2008
• What were the major features?
  • Tasks, better support for loop parallelism and nested parallelism

OpenMP 3.1

• When was it standardized?
  • 2011
• What was the major feature?
  • A mechanism to bind threads to processors.
  • Additions to support optimizations within the OpenMP tasking model.
  • The addition of predefined min and max reduction operators for C++ and C.
  • Extensions to the atomic construct to allow the value of the updated variable to be captured or overwritten.

OpenMP 4.0

• When was it standardized?
  • 2013
• What were the major features?
  • Offloading support - GPUs, Xeon Phis...
    • Mechanisms to describe regions of code where data and/or computation should be moved to another computing device
    • Breaks shared memory concept per se
  • SIMD constructs
    • New directives
      • Mark a loop to be executed using SIMD
      • Declare a function that can process multiple arguments using SIMD instructions
      • Marks a loop for thread work-sharing as well as SIMDing
  • Thread affinity - tell where to execute threads

OpenMP 4.5

• When was it standardized?
  • 2016
• What were the major features?
  • Task Loop Construct - divide iterations of a loop into tasks
  • Changes in data sharing and offloading

OpenMP 5.0

• When was it standardized?
  • TBD
• What were the major features?
  • TBD

See also

• MPI