.TH NAG_MPI_UN 3NAG .SH NAME nag_mpi_un \- NAG Parallel Library (MPI-based version), Release 2, Users' Note .ce 7 .B "NAG Parallel Library (MPI-based version), Release 2 .B "FDIB202DML - License Managed .B "IBM SP2 .B "Users' Note .SH "Introduction" This document is essential reading for every user of the NAG Parallel Library implementation specified in the title. It provides implementation-specific detail that augments the information provided in the NAG Parallel Library Manual. NAG recommends that users read the following minimum reference material before calling any library routine: .in +5 .ti -4 (a) Essential Introduction .ti -4 (b) Tutorial (MPI version) .ti -4 (c) Chapter Introduction .ti -4 (d) Implementation-specific Users' Note .in -5 Items (a), (b) and (c) are included in the NAG Parallel Library Manual; item (d) is this document. Each NAG Parallel Library site is supplied with at least one copy of each of the above. A postscript version of (a) and (b) and a Unix man version of (d) are available. .SH "General Information" .SS "IBM Parallel Environment" Parallel programs using the NAG Parallel Library require the IBM Parallel Environment to be installed on an SP series computer. The Parallel Environment enables a partition, which consists of a group of processor nodes, to be handled as an independent distributed memory parallel computer. A crucial component of the Parallel Environment is the `poe' command, which can be used to run parallel programs on multiple nodes of a partition using different communication modes. The Parallel Environment also provides several runtime libraries to support the execution of parallel programs. In particular, the Parallel Environment message-passing kernel library enables concurrent processes to communicate using either .nf (a) a simple, High Performance Switch (HPS) dedicated protocol - this is referred to as `user space' communication mode and is available on the IBM SP series of parallel computers, or (b) a TCP/IP protocol - this is referred to as `IP' communication mode and is available on a network of RISC System/6000 computers as well as the SP2 .fi Using the `user space' communication mode enables programs to access the HPS communication network directly without any system call. While this maximizes the performance of communication operations, it also restricts the number of processes on any processor node to only one. Using the `IP' communication mode results in slower communication operations, but enables multiple processes to run on a node simultaneously. Additionally, networks other than the HPS - for example, Ethernet - can be used with the `IP' communication mode. Further information on the IBM Parallel Environment can be found in the Parallel Environment Operation and Use Guide. In addition to the Parallel Environment, parallel programs using the NAG Parallel Library require the IBM implementation of MPI to be installed. IBM MPI is based on the message-passing kernel library supplied as part of the Parallel Environment and thus can be used in both `user space' and `IP' communication modes. The NAG Parallel Library has been tested and can be used with both `user space' and `IP' communication modes, and in the latter case both the HPS and Ethernet can be used as interconnection networks. .SS "Accessing the Library" The NAG Parallel Library consists of six different libraries. Assuming that libnagmpi.a, libnagmpiz.a, libnagpblas.a, libnagmpiblacs.a, libnagtools.a and libnagfls.a have been installed in a directory in the search path of the linker then a user may link to the NAG Parallel Library as follows: .nf mpxlf driver.f -lnagmpi -lnagpblas -lnagmpiz -lnagtools \ -lnagmpiblacs -lnagfls .fi where driver.f is the user's application program. .SS "Running NAG Parallel Library Programs" The `poe' command can to be used to run a user program, say a.out, linked with the NAG Parallel Library on multiple nodes of a partition in an IBM SP2, e.g. poe a.out -rmpool 0 -procs 4 instructs the system to execute the executable program a.out in four parallel processes. The nodes of an IBM SP2 are typically divided into pools, the -rmpool option specified the pool from which nodes will be automatically selected. Furthermore, the `poe' options `-euilib us' or `-euilib ip' can be used to choose the `user space' or `IP' communication modes, respectively. If neither of these options is used, the default communication mode `IP' is selected automatically. Note that selecting the `user space' communication mode limits the number of parallel processes to the number of processor nodes exclusively available to the user program. More detailed information on the `poe' command can be found in the Parallel Environment Operation and Use Guide. .SS "Optimizing Performance" The NAG Parallel Library uses standard sequential software components, such as the Basic Linear Algebra Subroutines (BLAS), wherever suitable. While the NAG Parallel Library provides portable implementations of these components, significant performance gains can often be attained by linking the user program with machine-optimized implementations. For instance, if the IBM ESSL Library is available on a system, it can be linked with the user program using the `-lessl' compiler option. .SS "Notes" The standard input, standard output and standard error output of the parallel program execution command `poe' are connected to all processes performing a NAG Parallel Library program. However, these connections are guaranteed only from the initial call of the NAG Parallel Library routine Z01AAFP until the final call of Z01ABFP. Read/write operations from/to standard input/output before the initial call of Z01AAFP and after the final call of Z01ABFP may fail. It is therefore recommended to call Z01AAFP at the very beginning and Z01ABFP at the very end of the user program. .SS "Example Programs" The example programs and data and the results obtained during the preparation of this specific implementation are supplied so you can try them yourself, or use one as a template for your own program. Note that the example material has been adapted, if necessary, from that printed in the NAG Parallel Library Manual, so that programs are suitable for execution with this implementation. The example programs are most easily accessed by using the script `runex', which will copy an example program and its data, compile it, link it with the libraries and run it. For example, give the command runex f04ebfp to run the F04EBFP example program. This will place the results in the subdirectory examples/newresults. .SS "On-line User Documentation" The following information is available in man page form: Users' Note - nag_mpi_un.3 The following information is available as ASCII files: .nf List of Contents - contents.ascii Reserved Names - reserved.ascii .fi The following information is available in postscript form: .nf Release 2 News - news.ps Future Developments - future.ps Essential Introduction - essint.ps Tutorial - tutorial.ps (step by step instructions for using the NAG Parallel Library) .fi .SH "Routine-specific Information" .ti -4 (a) X02 The constants referred to in the NAG Parallel Library Manual have the following values in this implementation: The values of the machine constants are: The basic parameters of the model .nf .in +4 X02BHF = 2 X02BJF = 53 X02BKF = -1021 X02BLF = 1024 X02DJF = .TRUE. .in -4 Derived parameters of floating-point arithmetic .in +4 X02AJF = 1.11022302462516D-16 X02AKF = 2.22507385850721D-308 X02ALF = 1.79769313486231D+308 X02AMF = 2.22507385850721D-308 X02ANF = 2.22507385850721D-308 .in -4 Parameters of other aspects of the computing environment .in +4 X02AHF = 8.11296384146067+31 X02BBF = 2147483647 X02BEF = 15 X02DAF = .FALSE. .in -4 .fi .SH "Additional Services from NAG" .ti -4 (a) Documentation Each NAG Parallel Library site is provided with a printed copy of the NAG Parallel Library Manual. Additional manuals are available at prices published in the NAG documentation order form. The NAG Parallel Library is also supported by a Hypertext system at extra cost which allows the user to browse through the Library documentation. Users will be advised of the availability of this system for different platforms as they become available. If you require further information please contact NAG. .SH "Support from NAG" .ti -4 (a) Contact with NAG Queries concerning this document or the implementation generally should be directed initially to your local Advisory Service. If you have difficulty in making contact locally, you can write to NAG directly, at one of the supplied addresses. Users subscribing to the support service are encouraged to contact one of the NAG Response Centres (see below). .ti -4 (b) NAG Response Centres The NAG Response Centres are available for general enquiries from all users and also for technical queries from sites with an annually licensed product or support service. The Response Centres are open during office hours, but contact is possible by fax, email and phone (answering machine) at all times. When contacting a Response Centre please quote your NAG user reference and NAG product code. .ti -4 (c) Network Network, NAG's newsletter, is produced periodically and sent free of charge to sites with a supported product or service. .ti -4 (d) NAG Website The NAG Website is an information service providing items of interest to users and prospective users of NAG products and services. The information is regularly updated and reviewed and includes implementation availability, descriptions of products, downloadable software and technical reports. The NAG Website can be accessed at .nf http://www.nag.co.uk/ or http://www.nag.com/ (in the USA) .fi .SH "NAG Users Association" NAGUA, the NAG Users Association, is a self-financing, non-profitmaking body. It exists to promote communications between NAG and users of its products and services. It provides information to NAG on the requirements of users, who are in turn kept informed of developments in services. Membership is available to any institution or individual holding a licence for any NAG product or service. Members receive discounts on the registration fees at conferences and workshops. For an information pack and membership application form, please contact NAGUA at the supplied address. .SH "Appendix - supplied addresses" .nf NAG Ltd Wilkinson House Jordan Hill Road OXFORD OX2 8DR NAG Ltd Response Centre United Kingdom email: support@nag.co.uk Tel: +44 (0)1865 511245 Tel: +44 (0)1865 311744 Fax: +44 (0)1865 310139 Fax: +44 (0)1865 310139 NAG Inc 1400 Opus Place, Suite 200 Downers Grove IL 60515-5702 NAG Inc Response Center USA email: infodesk@nag.com Tel: +1 630 971 2337 Tel: +1 630 971 2345 Fax: +1 630 971 2706 Fax: +1 630 971 2346 Nihon NAG KK Yaesu Nagaoka Building No. 6 1-9-8 Minato Chuo-ku Tokyo Japan email: help@nag-j.co.jp Tel: +81 3 5542 6311 Fax: +81 3 5542 631