# Toward a Standard Interface for User-Defined Scheduling in OpenMP

## TL;DR

This paper proposes extending OpenMP to support user-defined scheduling strategies, enabling more flexible and application-specific parallel loop performance improvements.

## Contribution

It introduces two candidate interfaces for user-defined scheduling in OpenMP, facilitating standard compliance and customization.

## Key findings

- Two competing interfaces are proposed for user-defined scheduling.
- Conceptual comparison across C, C++, and Fortran.
- Framework serves as a basis for discussion and prototyping.

## Abstract

Parallel loops are an important part of OpenMP programs. Efficient scheduling of parallel loops can improve performance of the programs. The current OpenMP specification only offers three options for loop scheduling, which are insufficient in certain instances. Given the large number of other possible scheduling strategies, it is infeasible to standardize each one. A more viable approach is to extend the OpenMP standard to allow for users to define loop scheduling strategies. The approach will enable standard-compliant application-specific scheduling. This work analyzes the principal components required by user-defined scheduling and proposes two competing interfaces as candidates for the OpenMP standard. We conceptually compare the two proposed interfaces with respect to the three host languages of OpenMP, i.e., C, C++, and Fortran. These interfaces serve the OpenMP community as a basis for discussion and prototype implementation for user-defined scheduling.