- •Contents
- •List of Figures
- •List of Tables
- •Acknowledgments
- •Introduction to MPI
- •Overview and Goals
- •Background of MPI-1.0
- •Background of MPI-1.1, MPI-1.2, and MPI-2.0
- •Background of MPI-1.3 and MPI-2.1
- •Background of MPI-2.2
- •Who Should Use This Standard?
- •What Platforms Are Targets For Implementation?
- •What Is Included In The Standard?
- •What Is Not Included In The Standard?
- •Organization of this Document
- •MPI Terms and Conventions
- •Document Notation
- •Naming Conventions
- •Semantic Terms
- •Data Types
- •Opaque Objects
- •Array Arguments
- •State
- •Named Constants
- •Choice
- •Addresses
- •Language Binding
- •Deprecated Names and Functions
- •Fortran Binding Issues
- •C Binding Issues
- •C++ Binding Issues
- •Functions and Macros
- •Processes
- •Error Handling
- •Implementation Issues
- •Independence of Basic Runtime Routines
- •Interaction with Signals
- •Examples
- •Point-to-Point Communication
- •Introduction
- •Blocking Send and Receive Operations
- •Blocking Send
- •Message Data
- •Message Envelope
- •Blocking Receive
- •Return Status
- •Passing MPI_STATUS_IGNORE for Status
- •Data Type Matching and Data Conversion
- •Type Matching Rules
- •Type MPI_CHARACTER
- •Data Conversion
- •Communication Modes
- •Semantics of Point-to-Point Communication
- •Buffer Allocation and Usage
- •Nonblocking Communication
- •Communication Request Objects
- •Communication Initiation
- •Communication Completion
- •Semantics of Nonblocking Communications
- •Multiple Completions
- •Non-destructive Test of status
- •Probe and Cancel
- •Persistent Communication Requests
- •Send-Receive
- •Null Processes
- •Datatypes
- •Derived Datatypes
- •Type Constructors with Explicit Addresses
- •Datatype Constructors
- •Subarray Datatype Constructor
- •Distributed Array Datatype Constructor
- •Address and Size Functions
- •Lower-Bound and Upper-Bound Markers
- •Extent and Bounds of Datatypes
- •True Extent of Datatypes
- •Commit and Free
- •Duplicating a Datatype
- •Use of General Datatypes in Communication
- •Correct Use of Addresses
- •Decoding a Datatype
- •Examples
- •Pack and Unpack
- •Canonical MPI_PACK and MPI_UNPACK
- •Collective Communication
- •Introduction and Overview
- •Communicator Argument
- •Applying Collective Operations to Intercommunicators
- •Barrier Synchronization
- •Broadcast
- •Example using MPI_BCAST
- •Gather
- •Examples using MPI_GATHER, MPI_GATHERV
- •Scatter
- •Examples using MPI_SCATTER, MPI_SCATTERV
- •Example using MPI_ALLGATHER
- •All-to-All Scatter/Gather
- •Global Reduction Operations
- •Reduce
- •Signed Characters and Reductions
- •MINLOC and MAXLOC
- •All-Reduce
- •Process-local reduction
- •Reduce-Scatter
- •MPI_REDUCE_SCATTER_BLOCK
- •MPI_REDUCE_SCATTER
- •Scan
- •Inclusive Scan
- •Exclusive Scan
- •Example using MPI_SCAN
- •Correctness
- •Introduction
- •Features Needed to Support Libraries
- •MPI's Support for Libraries
- •Basic Concepts
- •Groups
- •Contexts
- •Intra-Communicators
- •Group Management
- •Group Accessors
- •Group Constructors
- •Group Destructors
- •Communicator Management
- •Communicator Accessors
- •Communicator Constructors
- •Communicator Destructors
- •Motivating Examples
- •Current Practice #1
- •Current Practice #2
- •(Approximate) Current Practice #3
- •Example #4
- •Library Example #1
- •Library Example #2
- •Inter-Communication
- •Inter-communicator Accessors
- •Inter-communicator Operations
- •Inter-Communication Examples
- •Caching
- •Functionality
- •Communicators
- •Windows
- •Datatypes
- •Error Class for Invalid Keyval
- •Attributes Example
- •Naming Objects
- •Formalizing the Loosely Synchronous Model
- •Basic Statements
- •Models of Execution
- •Static communicator allocation
- •Dynamic communicator allocation
- •The General case
- •Process Topologies
- •Introduction
- •Virtual Topologies
- •Embedding in MPI
- •Overview of the Functions
- •Topology Constructors
- •Cartesian Constructor
- •Cartesian Convenience Function: MPI_DIMS_CREATE
- •General (Graph) Constructor
- •Distributed (Graph) Constructor
- •Topology Inquiry Functions
- •Cartesian Shift Coordinates
- •Partitioning of Cartesian structures
- •Low-Level Topology Functions
- •An Application Example
- •MPI Environmental Management
- •Implementation Information
- •Version Inquiries
- •Environmental Inquiries
- •Tag Values
- •Host Rank
- •IO Rank
- •Clock Synchronization
- •Memory Allocation
- •Error Handling
- •Error Handlers for Communicators
- •Error Handlers for Windows
- •Error Handlers for Files
- •Freeing Errorhandlers and Retrieving Error Strings
- •Error Codes and Classes
- •Error Classes, Error Codes, and Error Handlers
- •Timers and Synchronization
- •Startup
- •Allowing User Functions at Process Termination
- •Determining Whether MPI Has Finished
- •Portable MPI Process Startup
- •The Info Object
- •Process Creation and Management
- •Introduction
- •The Dynamic Process Model
- •Starting Processes
- •The Runtime Environment
- •Process Manager Interface
- •Processes in MPI
- •Starting Processes and Establishing Communication
- •Reserved Keys
- •Spawn Example
- •Manager-worker Example, Using MPI_COMM_SPAWN.
- •Establishing Communication
- •Names, Addresses, Ports, and All That
- •Server Routines
- •Client Routines
- •Name Publishing
- •Reserved Key Values
- •Client/Server Examples
- •Ocean/Atmosphere - Relies on Name Publishing
- •Simple Client-Server Example.
- •Other Functionality
- •Universe Size
- •Singleton MPI_INIT
- •MPI_APPNUM
- •Releasing Connections
- •Another Way to Establish MPI Communication
- •One-Sided Communications
- •Introduction
- •Initialization
- •Window Creation
- •Window Attributes
- •Communication Calls
- •Examples
- •Accumulate Functions
- •Synchronization Calls
- •Fence
- •General Active Target Synchronization
- •Lock
- •Assertions
- •Examples
- •Error Handling
- •Error Handlers
- •Error Classes
- •Semantics and Correctness
- •Atomicity
- •Progress
- •Registers and Compiler Optimizations
- •External Interfaces
- •Introduction
- •Generalized Requests
- •Examples
- •Associating Information with Status
- •MPI and Threads
- •General
- •Initialization
- •Introduction
- •File Manipulation
- •Opening a File
- •Closing a File
- •Deleting a File
- •Resizing a File
- •Preallocating Space for a File
- •Querying the Size of a File
- •Querying File Parameters
- •File Info
- •Reserved File Hints
- •File Views
- •Data Access
- •Data Access Routines
- •Positioning
- •Synchronism
- •Coordination
- •Data Access Conventions
- •Data Access with Individual File Pointers
- •Data Access with Shared File Pointers
- •Noncollective Operations
- •Collective Operations
- •Seek
- •Split Collective Data Access Routines
- •File Interoperability
- •Datatypes for File Interoperability
- •Extent Callback
- •Datarep Conversion Functions
- •Matching Data Representations
- •Consistency and Semantics
- •File Consistency
- •Random Access vs. Sequential Files
- •Progress
- •Collective File Operations
- •Type Matching
- •Logical vs. Physical File Layout
- •File Size
- •Examples
- •Asynchronous I/O
- •I/O Error Handling
- •I/O Error Classes
- •Examples
- •Subarray Filetype Constructor
- •Requirements
- •Discussion
- •Logic of the Design
- •Examples
- •MPI Library Implementation
- •Systems with Weak Symbols
- •Systems Without Weak Symbols
- •Complications
- •Multiple Counting
- •Linker Oddities
- •Multiple Levels of Interception
- •Deprecated Functions
- •Deprecated since MPI-2.0
- •Deprecated since MPI-2.2
- •Language Bindings
- •Overview
- •Design
- •C++ Classes for MPI
- •Class Member Functions for MPI
- •Semantics
- •C++ Datatypes
- •Communicators
- •Exceptions
- •Mixed-Language Operability
- •Problems With Fortran Bindings for MPI
- •Problems Due to Strong Typing
- •Problems Due to Data Copying and Sequence Association
- •Special Constants
- •Fortran 90 Derived Types
- •A Problem with Register Optimization
- •Basic Fortran Support
- •Extended Fortran Support
- •The mpi Module
- •No Type Mismatch Problems for Subroutines with Choice Arguments
- •Additional Support for Fortran Numeric Intrinsic Types
- •Language Interoperability
- •Introduction
- •Assumptions
- •Initialization
- •Transfer of Handles
- •Status
- •MPI Opaque Objects
- •Datatypes
- •Callback Functions
- •Error Handlers
- •Reduce Operations
- •Addresses
- •Attributes
- •Extra State
- •Constants
- •Interlanguage Communication
- •Language Bindings Summary
- •Groups, Contexts, Communicators, and Caching Fortran Bindings
- •External Interfaces C++ Bindings
- •Change-Log
- •Bibliography
- •Examples Index
- •MPI Declarations Index
- •MPI Function Index
10.4. ESTABLISHING COMMUNICATION |
325 |
MPI_LOOKUP_NAME(service_name, info, port_name)
IN |
service_name |
a service name (string) |
IN |
info |
implementation-speci c information (handle) |
OUT |
port_name |
a port name (string) |
int MPI_Lookup_name(char *service_name, MPI_Info info, char *port_name)
MPI_LOOKUP_NAME(SERVICE_NAME, INFO, PORT_NAME, IERROR)
CHARACTER*(*) SERVICE_NAME, PORT_NAME
INTEGER INFO, IERROR
fvoid MPI::Lookup_name(const char* service_name, const MPI::Info& info, char* port_name) (binding deprecated, see Section 15.2) g
This function retrieves a port_name published by MPI_PUBLISH_NAME with service_name. If service_name has not been published, it raises an error in the error class MPI_ERR_NAME. The application must supply a port_name bu er large enough to hold the largest possible port name (see discussion above under MPI_OPEN_PORT).
If an implementation allows multiple entries with the same service_name within the same scope, a particular port_name is chosen in a way determined by the implementation.
If the info argument was used with MPI_PUBLISH_NAME to tell the implementation how to publish names, a similar info argument may be required for MPI_LOOKUP_NAME.
10.4.5 Reserved Key Values
The following key values are reserved. An implementation is not required to interpret these key values, but if it does interpret the key value, it must provide the functionality described.
ip_port Value contains IP port number at which to establish a port. (Reserved for
MPI_OPEN_PORT only).
ip_address Value contains IP address at which to establish a port. If the address is not a valid IP address of the host on which the MPI_OPEN_PORT call is made, the results are unde ned. (Reserved for MPI_OPEN_PORT only).
10.4.6 Client/Server Examples
Simplest Example | Completely Portable.
The following example shows the simplest way to use the client/server interface. It does not use service names at all.
On the server side:
char myport[MPI_MAX_PORT_NAME]; MPI_Comm intercomm;
/* ... */ MPI_Open_port(MPI_INFO_NULL, myport); printf("port name is: %s\n", myport);
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326 |
CHAPTER 10. PROCESS CREATION AND MANAGEMENT |
1MPI_Comm_accept(myport, MPI_INFO_NULL, 0, MPI_COMM_SELF, &intercomm);
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/* do something with intercomm */
4The server prints out the port name to the terminal and the user must type it in when
5starting up the client (assuming the MPI implementation supports stdin such that this
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works). On the client side:
MPI_Comm intercomm;
char name[MPI_MAX_PORT_NAME]; printf("enter port name: "); gets(name);
MPI_Comm_connect(name, MPI_INFO_NULL, 0, MPI_COMM_SELF, &intercomm);
Ocean/Atmosphere - Relies on Name Publishing
15In this example, the \ocean" application is the \server" side of a coupled ocean-atmosphere
16climate model. It assumes that the MPI implementation publishes names.
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19MPI_Open_port(MPI_INFO_NULL, port_name);
20MPI_Publish_name("ocean", MPI_INFO_NULL, port_name);
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22MPI_Comm_accept(port_name, MPI_INFO_NULL, 0, MPI_COMM_SELF, &intercomm);
23/* do something with intercomm */
24MPI_Unpublish_name("ocean", MPI_INFO_NULL, port_name);
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MPI_Lookup_name("ocean", MPI_INFO_NULL, port_name); MPI_Comm_connect( port_name, MPI_INFO_NULL, 0, MPI_COMM_SELF,
&intercomm);
Simple Client-Server Example.
34This is a simple example; the server accepts only a single connection at a time and serves
35that connection until the client requests to be disconnected. The server is a single process.
36Here is the server. It accepts a single connection and then processes data until it
37receives a message with tag 1. A message with tag 0 tells the server to exit.
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39#include "mpi.h"
40int main( int argc, char **argv )
41{
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MPI_Comm client;
MPI_Status status;
char port_name[MPI_MAX_PORT_NAME];
double |
buf[MAX_DATA]; |
int |
size, again; |
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48 MPI_Init( &argc, &argv );
10.4. ESTABLISHING COMMUNICATION |
327 |
MPI_Comm_size(MPI_COMM_WORLD, &size);
if (size != 1) error(FATAL, "Server too big"); MPI_Open_port(MPI_INFO_NULL, port_name); printf("server available at %s\n",port_name); while (1) {
MPI_Comm_accept( port_name, MPI_INFO_NULL, 0, MPI_COMM_WORLD, &client );
again = 1; while (again) {
MPI_Recv( buf, MAX_DATA, MPI_DOUBLE,
MPI_ANY_SOURCE, MPI_ANY_TAG, client, &status ); switch (status.MPI_TAG) {
case 0: MPI_Comm_free( &client ); MPI_Close_port(port_name); MPI_Finalize();
return 0;
case 1: MPI_Comm_disconnect( &client ); again = 0;
break;
case 2: /* do something */
...
default:
/* Unexpected message type */ MPI_Abort( MPI_COMM_WORLD, 1 );
}
}
}
}
Here is the client.
#include "mpi.h"
int main( int argc, char **argv )
{
MPI_Comm server; double buf[MAX_DATA];
char port_name[MPI_MAX_PORT_NAME];
MPI_Init( &argc, &argv );
strcpy(port_name, argv[1] );/* assume server's name is cmd-line arg */
MPI_Comm_connect( port_name, MPI_INFO_NULL, 0, MPI_COMM_WORLD, &server );
while (!done) {
tag = 2; /* Action to perform */
MPI_Send( buf, n, MPI_DOUBLE, 0, tag, server ); /* etc */
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