Role-shifting threads: Increasing OpenMP malleability to address load imbalance at MPI and OpenMP

This paper presents the evolution of the free agent threads for OpenMP to the new role-shifting threads model and their integration with the Dynamic Load Balancing (DLB) library. We demonstrate how free agent threads can improve resource utilization in OpenMP applications with load imbalance in their nested parallel regions. We also demonstrate how DLB efficiently manages the malleability exposed by the role-shifting threads to address load imbalance issues. We use three real-world scientific applications, one of them to demonstrate that free agents alone can improve the OpenMP model without external tools, and two other MPI+OpenMP applications, one of them with a coupling case, to illustrate the potential of the free agent threads’ malleability with an external resource manager to increase the efficiency of the system. In addition, we demonstrate that the new implementation is more usable than the former one, letting the runtime system automatically make decisions that were made by the programmer previously. All software is released open-source.This work has received funding from the DEEP Projects, at the European Commission’s FP7, H2020, and EuroHPC Programmes, under Grant Agreements 287530, 610476, 754304, and 955606. The PCI2021-121958 financed by the Spanish State Research Agency - Ministry of Science and Innovation. And it also has the support of the Spanish Ministry of Science and Innovation (Computacion de Altas Prestaciones VIII: PID2019-107255GB).Peer ReviewedPostprint (author's final draft

Performance analysis and optimization of an HPC application: DMRG++

DMRG++ (Density Matrix Renormalization Group) és una aplicació de física de la matèria condensada orientada a HPC, originalment desenvolupada per l'Oak Ridge National Laboratory (ORNL). En aquest projecte es treballarà en la millora de la part de càlcul intensiu de l'aplicació, fent ús d'una miniapp que encapsula aquesta secció crítica. Partint d'una implementació inicial amb OpenMP basada en diversos parallel for aniuats, s'exploraran diferents alternatives per millorar el temps d'execució i el consum de memòria mitjançant el model de tasques amb dependències d'OpenMP, tot fent servir una estratègia d'anàlisi de l'aplicació i de desenvolupament iterativa. D'aquesta manera, no només esperem contribuir amb la millora d'una aplicació científica, sinó també mostrar tècniques d'anàlisi efectives i estratègies de paral·lelització per a aplicacions amb distribucions de feina molt desiguals.DMRG++ (Density Matrix Renormalization Group) is a condensed matter physics application oriented to HPC, developed by Oak Ridge National Laboratory (ORNL). In this project, we will focus on improving the intensive arithmetic kernel of the application, using a miniapp that encapsulates this critical program part. Starting with an initial implementation with OpenMP, which uses several nested parallel for, we will explore different alternatives to improve its execution time and memory consumption through OpenMP task dependency model, taking advantage of an iterative strategy of in-depth application analysis and development. In this way, we are not just contributing by improving a scientific application, but also showing effective analysis techniques and best practices for programmability and parallelization focused on applications with irregular workloads

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described