- •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
274 |
CHAPTER 8. MPI ENVIRONMENTAL MANAGEMENT |
19 in rack 4 of mpp.cs.org" and \231" (where 231 is the actual processor number in the
2running homogeneous system). The argument name must represent storage that is at least
3MPI_MAX_PROCESSOR_NAME characters long. MPI_GET_PROCESSOR_NAME may write
4up to this many characters into name.
5The number of characters actually written is returned in the output argument, resultlen.
6In C, a null character is additionally stored at name[resultlen]. The resultlen cannot be larger
7then MPI_MAX_PROCESSOR_NAME-1. In Fortran, name is padded on the right with blank
8characters. The resultlen cannot be larger then MPI_MAX_PROCESSOR_NAME.
9
10Rationale. This function allows MPI implementations that do process migration to
11return the current processor. Note that nothing in MPI requires or de nes process
12migration; this de nition of MPI_GET_PROCESSOR_NAME simply allows such an
13implementation. (End of rationale.)
14
15Advice to users. The user must provide at least MPI_MAX_PROCESSOR_NAME space
16to write the processor name | processor names can be this long. The user should
17examine the output argument, resultlen, to determine the actual length of the name.
18(End of advice to users.)
19
20The constant MPI_BSEND_OVERHEAD provides an upper bound on the xed overhead
21per message bu ered by a call to MPI_BSEND (see Section 3.6.1).
22
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8.2 Memory Allocation |
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25In some systems, message-passing and remote-memory-access (RMA) operations run faster
26when accessing specially allocated memory (e.g., memory that is shared by the other pro-
27cesses in the communicating group on an SMP). MPI provides a mechanism for allocating
28and freeing such special memory. The use of such memory for message-passing or RMA is not
29mandatory, and this memory can be used without restrictions as any other dynamically allo-
30cated memory. However, implementations may restrict the use of the MPI_WIN_LOCK and
31MPI_WIN_UNLOCK functions to windows allocated in such memory (see Section 11.4.3.)
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MPI_ALLOC_MEM(size, info, baseptr)
IN |
size |
size of memory segment in bytes (non-negative inte- |
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ger) |
IN |
info |
info argument (handle) |
OUT |
baseptr |
pointer to beginning of memory segment allocated |
41 int MPI_Alloc_mem(MPI_Aint size, MPI_Info info, void *baseptr)
42
MPI_ALLOC_MEM(SIZE, INFO, BASEPTR, IERROR)
43
INTEGER INFO, IERROR
44
INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR
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fvoid* MPI::Alloc_mem(MPI::Aint size, const MPI::Info& info) (binding |
47 |
deprecated, see Section 15.2) g |
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8.2. MEMORY ALLOCATION |
275 |
The info argument can be used to provide directives that control the desired location of the allocated memory. Such a directive does not a ect the semantics of the call. Valid info values are implementation-dependent; a null directive value of info = MPI_INFO_NULL is always valid.
The function MPI_ALLOC_MEM may return an error code of class MPI_ERR_NO_MEM to indicate it failed because memory is exhausted.
MPI_FREE_MEM(base)
IN |
base |
initial address of memory segment allocated by |
|
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MPI_ALLOC_MEM (choice) |
int MPI_Free_mem(void *base)
MPI_FREE_MEM(BASE, IERROR) <type> BASE(*)
INTEGER IERROR
fvoid MPI::Free_mem(void *base) (binding deprecated, see Section 15.2) g
The function MPI_FREE_MEM may return an error code of class MPI_ERR_BASE to indicate an invalid base argument.
Rationale. The C and C++ bindings of MPI_ALLOC_MEM and MPI_FREE_MEM are similar to the bindings for the malloc and free C library calls: a call to
MPI_Alloc_mem(..., &base) should be paired with a call to MPI_Free_mem(base) (one less level of indirection). Both arguments are declared to be of same type void* so as to facilitate type casting. The Fortran binding is consistent with the C and C++ bindings: the Fortran MPI_ALLOC_MEM call returns in baseptr the (integer valued) address of the allocated memory. The base argument of MPI_FREE_MEM is a choice argument, which passes (a reference to) the variable stored at that location. (End of rationale.)
Advice to implementors. If MPI_ALLOC_MEM allocates special memory, then a design similar to the design of C malloc and free functions has to be used, in order to nd out the size of a memory segment, when the segment is freed. If no special memory is used, MPI_ALLOC_MEM simply invokes malloc, and MPI_FREE_MEM invokes free.
A call to MPI_ALLOC_MEM can be used in shared memory systems to allocate memory in a shared memory segment. (End of advice to implementors.)
Example 8.1 Example of use of MPI_ALLOC_MEM, in Fortran with pointer support. We assume 4-byte REALs, and assume that pointers are address-sized.
REAL A
POINTER (P, A(100,100)) ! no memory is allocated CALL MPI_ALLOC_MEM(4*100*100, MPI_INFO_NULL, P, IERR) ! memory is allocated
...
A(3,5) = 2.71;
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