Message Passing Interface Forum Research Articles

An international survey on MPI users

The Message Passing Interface (MPI) plays a crucial part in the parallel computing ecosystem, a driving force behind many of the high-performance computing (HPC) successes. To maintain its relevance to the user community—and in particular to the growing HPC community at large—the MPI standard needs to identify and understand the MPI users’ concerns and expectations, and adapt accordingly to continue to efficiently bridge the gap between users and hardware. This questionnaire survey was conducted using two online questionnaire frameworks and has gathered more than 850 answers from 42 countries since February 2019. Some of preceding surveys of MPI uses are questionnaire surveys like ours, while others are conducted either by analyzing MPI programs to reveal static behavior or by using profiling tools to analyze the dynamic runtime behavior of MPI jobs. Our survey is different from other questionnaire surveys in terms of its larger number of participants and wide geographic spread. As a result, it is possible to illustrate the current status of MPI users more accurately and with a wider geographical distribution. In this report, we will show some interesting findings, compare the results with preceding studies when possible, and provide some recommendations for MPI Forum based on the findings.

Fault tolerance of MPI applications in exascale systems: The ULFM solution

The growth in the number of computational resources used by high-performance computing (HPC) systems leads to an increase in failure rates. Fault-tolerant techniques will become essential for long-running applications executing in future exascale systems, not only to ensure the completion of their execution in these systems but also to improve their energy consumption. Although the Message Passing Interface (MPI) is the most popular programming model for distributed-memory HPC systems, as of now, it does not provide any fault-tolerant construct for users to handle failures. Thus, the recovery procedure is postponed until the application is aborted and re-spawned. The proposal of the User Level Failure Mitigation (ULFM) interface in the MPI forum provides new opportunities in this field, enabling the implementation of resilient MPI applications, system runtimes, and programming language constructs able to detect and react to failures without aborting their execution. This paper presents a global overview of the resilience interfaces provided by the ULFM specification, covers archetypal usage patterns and building blocks, and surveys the wide variety of application-driven solutions that have exploited them in recent years. The large and varied number of approaches in the literature proves that ULFM provides the necessary flexibility to implement efficient fault-tolerant MPI applications. All the proposed solutions are based on application-driven recovery mechanisms, which allows reducing the overhead and obtaining the required level of efficiency needed in the future exascale platforms.

Extreme-scale computing services over MPI: Experiences, observations and features proposal for next-generation message passing interface

The message passing interface (MPI) is one of the most portable high-performance computing (HPC) programming models, with platform-optimized implementations typically delivered with new HPC systems. Therefore, for distributed services requiring portable, high-performance, user-level network access, MPI promises to be an attractive alternative to custom network portability layers, platform-specific methods, or portable but less performant interfaces such as BSD sockets. In this paper, we present our experiences in using MPI as a network transport for a large-scale distributed storage system. We discuss the features of MPI that facilitate adoption as well as aspects which require various workarounds. Based on use cases, we derive a wish list for both MPI implementations and the MPI forum to facilitate the adoption of MPI by large-scale persistent services. The proposals in the wish list go beyond the sole needs of distributed services; we contend that they will benefit mainstream HPC applications at extreme scales as well.

A high-performance, portable implementation of the MPI message passing interface standard

MPI (Message Passing Interface) is a specification for a standard library for message passing that was defined by the MPI Forum, a broadly based group of parallel computer vendors, library writers, and applications specialists. Multiple implementations of MPI have been developed. In this paper, we describe MPICH, unique among existing implementations in its design goal of combining portability with high performance. We document its portability and performance and describe the architecture by which these features are simultaneously achieved. We also discuss the set of tools that accompany the free distribution of MPICH, which constitute the beginnings of a portable parallel programming environment. A project of this scope inevitably imparts lessons about parallel computing, the specification being followed, the current hardware and software environment for parallel computing, and project management; we describe those we have learned. Finally, we discuss future developments for MPICH, including those necessary to accommodate extensions to the MPI Standard now being contemplated by the MPI Forum.