A user's guide to PICL a portable instrumented communication library

Abstract

This report is the PICL user's guide, lt contains an overview of PICL and how it is used. Examples in C and Fortran are included. PICL is a subroutine library that can be used to develop parallel programs that are portable across several distributed-memory multiprocessors. P1CL provides a portable syntax for key communication primitives and related system calls. It also provides portable routines to perform certain widely-used, high-level communication operations, such as global broadcast and global summation. Finally, PICL provides execution tracing that can be used to monitor performance or to aid in debugging.-V-This document contains examples and information needed for straightibrward use of most of PICL's basic features. Full documentation of all PICL options and the various ways the library can be used is contained in a separate report [1]. The library is made up of three distinct sets of routines: a set of low-level communication and system primitives described in section 2, a set of high-level global communication routines whose use is described in section 3, and a set of routines for ,, invoking and controlling the execution tracing facility, whi(:h is described iii s(,(:tiozl 4. Each section __ntains examl)les in C sllowing typical uses oi' the resl)ectiw,_ routines. IIi. addition, tile Appendix contains FORTRAN versions of tile examples and instructions for obtaining PICL and ParaGraph. 2. Low-Level Routines The 12 low-level communication and system interface routines, described ill Table 1, provide a portable syntax for message-passing programs. Tile PICL programming model assumes that the multiI)rocessor can send messagt:s between arbitrarily chosen pairs of processors. The time required to send a message between two processors is a function of the interprocessor communication network, a.nd user will need to be aware of such machine dependencies in order to write efficient programs. Our model distinguishes one processor, the host, from the rest. The user has access to the remaining processors, called node processors (or simply nodes), through the host. Typically, an application code consists of one program that runs on the host ,, and another program that run,,',,on each of the nodes. The host program calls PICL routines to allocate node processors, load the node progi'am (or l_r0gra.ms) onto the nodes, send input data required by the node programs, a.nd receive results fronl thf, nodes.

Performance analysis of distributed applications using automatic classification of communication inefficiencies

“…Users may analyze these events at runtime or they may write these events to a log file for post-mortem analysis. Most trace-based performance analysis systems including PICL, Pablo, and Tau [8,18,21] use this approach. We choose tracing because it provides a chronological description of application events and consequently, it is more general than techniques such as profiling.…”

CCL: a portable and tunable collective communication library for scalable parallel computers

“…(This is usually done using a send-receive operation found in many parallel systems.) In most existing messagepassing parallel systems, the time for sending an m-byte message from process p to process q, without congestion, can , and the recently announced IBM's Scalable POWERparallel System 1 (SPl), and in environments such as Express [37], PARMACS [31], PICL [29], Zipcode [35] and Venus [4]. These systems and environments generally ignore the specific structure and topology of the communication network and assume a fully-connected collection of processes, in which each process can communicate directly with any other process by sending and receiving messages.…”

“…Over the past few years, a large number of programming environments and communication libraries for parallel computers have been developed, including PVM [8], Linda [16], PICL [29], PARMACS [31], Zipcode [35], Express [37], the nCUBE/2 library [34], the CM-5 library [36], and the iPSC/860 library. The design and implementation of the CCL adopts some of the popular communication concepts that already exist in many of these libraries, and, in addition, it provides several novel aspects.…”

Parallel and Distributed Algorithms for High-Speed Image Processing

“…The most widely used and well understood paradigm for the implementation of parallel programs on distributed memory architectures is that of message passing. Several message passing libraries are available in the public domain, including p4 [5], Parallel Virtual Machine (PVM) [3], PICL [10], and Zipcode [18]. Recently, a core of library routines (influenced strongly by existing libraries) has been standardized in the Message Passing Interface (MPI) [8,11,9].…”