测试Open MPI的安装

命令"ompi_info"可用来检测Open MPI的安装状态。该命令会返回

一个关于你的Open MPI安装的大概信息。

Note that the ompi_info command

is

extremely helpful in determining which components are installed as well

as

listing all the run-time settable parameters that are available in each

component (as well as their default values).

下列选项可能会有用：

--allShow a *lot* of information about your Open MPI installation.

--parsableDisplay all the information in an easily grep/cut/awk/sed-able

format.

--param

A of

"all" and a of "all" will show all

parameters to all components.Otherwise,

the parameters of all the components in a specific framework, or just

the

parameters of a specific component can be displayed by using an

appropriate

and/or name.

Changing the values of these

parameters is

explained in the "The Modular Component Architecture (MCA)" section,

below.

编译Open MPI应用

Open MPI提供了可用来编译MPI应用的"wrapper"编译器：

C:mpicc

C++:mpiCC (or mpic++ if your filesystem is case-insensitive)

Fortran 77: mpif77

Fortran 90: mpif90

例如：

shell$ mpicc hello_world_mpi.c

-o

hello_world_mpi -g

All the wrapper compilers do is

add a

variety of compiler and linker flags to the command line and then invoke

a

back-end compiler.To be specific: the

wrapper compilers do not parse source code at all; they are solely

command-line

manipulators, and have nothing to do with the actual compilation or

linking of

programs.The end result is an MPI executable

that is properly linked to all the relevant libraries.

运行Open MPI应用

Open MPI提供了mpirun和mpiexec(他们是相同的)。例如：

shell$ mpirun -np 2

hello_world_mpi

和

shell$ mpiexec -np 1

hello_world_mpi : -np

1 hello_world_mpi

是相同的。某些mpiexec的switches(比如-host和–arch)are not yet functional，

尽管在你使用它们时并不会发生错误。

The rsh launcher接受一个-hostfile参数(也可以使用选项"-machinefile"，两者是等价的)；你可以指定一个-hostfile参数来标志一个标准的mpirun-style

hostfile(每行一个主机名)：

shell$ mpirun -hostfile

my_hostfile -np 2

hello_world_mpi

如果你想在一个节点上运行多个进程，那么hostfile可以使用"slots"属性。如果没有指定"slots"，那么将假设其数目为1。例如，使用如下的hostfile：

---------------------------------------------------------------------------

node1.example.com

node2.example.com

node3.example.com slots=2

node4.example.com slots=4

---------------------------------------------------------------------------

shell$ mpirun -hostfile

my_hostfile -np 8

hello_world_mpi

will launch MPI_COMM_WORLD rank 0

on node1,

rank 1 on node2, ranks 2 and 3 on node3, and ranks 4 through 7 on node4.

Other starters, such as the

batch

scheduling environments, do not require hostfiles (and will ignore the

hostfile

if it is supplied). They will also launch as many processes as slots

have been

allocated by the scheduler if no "-np" argument has been

provided.For example, running an

interactive SLURM job with 8 processors:

shell$ srun -n 8 -A

shell$ mpirun a.out

The above command will launch 8

copies of

a.out in a single MPI_COMM_WORLD on the processors that were allocated

by

SLURM.

Note that the values of

component

parameters can be changed on the mpirun / mpiexec command line.This is explained in the section below,

"The Modular Component Architecture (MCA)".

The Modular Component Architecture (MCA)

The MCA is the backbone of Open

MPI -- most

services and functionality are implemented through MCA components.Here is a list of all the component frameworks

in Open MPI:

---------------------------------------------------------------------------

MPI组件框架：

-------------------------

allocator - Memory allocator

bml- BTL management layer

btl- MPI point-to-point byte transfer layer, used for MPI

point-to-point

messages on some types of networks

coll- MPI collective algorithms

io- MPI-2 I/O

mpool- Memory pooling

mtl- Matching transport layer, used for MPI point-to-point messages

on some

types of networks

osc- MPI-2 one-sided communications

pml- MPI point-to-point management layer

rcache- Memory registration cache

topo- MPI topology routines

Back-end run-time environment

component

frameworks:

---------------------------------------------------

errmgr- RTE error manager

gpr- General purpose registry

iof- I/O forwarding

ns- Name server

odls- OpenRTE daemon local launch subsystem

oob- Out of band messaging

pls- Process launch system

ras- Resource allocation system

rds- Resource discovery system

rmaps- Resource mapping system

rmgr- Resource manager

rml- RTE message layer

schema- Name schemas

sds- Startup / discovery service

smr- State-of-health monitoring subsystem

Miscellaneous frameworks:

-------------------------

backtrace - Debugging call stack

backtrace

support

maffinity - Memory affinity

memory- Memory subsystem hooks

memcpy- Memopy copy support

memory- Memory management hooks

paffinity - Processor affinity

timer- High-resolution timers

---------------------------------------------------------------------------

Each framework typically has one

or more

components that are used at run-time.For example, the btl framework is used by MPI to send bytes

across

underlying networks.The tcp btl, for

example, sends messages across TCP-based networks; the gm btl sends

messages

across GM Myrinet-based networks.

Each component typically has

some tunable

parameters that can be changed at run-time.Use the ompi_info command to check a component to see what its

tunable

parameters are.For example:

shell$ ompi_info --param btl tcp

shows all the parameters (and

default

values) for the tcp btl component.

These values can be overridden

at run-time

in several ways.At run-time, the

following locations are examined (in order) for new values of

parameters:

1.

/etc/openmpi-mca-params.conf

This file is intended to set any system-wide default MCA

parameter values

-- it will apply, by default, to all users who use this Open MPI

installation.The default file that is

installed contains many comments explaining its format.

2.

$HOME/.openmpi/mca-params.conf

If

this file exists, it should be in the same format as

/etc/openmpi-mca-params.conf.It is intended to provide per-user default parameter values.

3. environment variables of the

form

OMPI_MCA_ set equal to a

Where is the name of the parameter.For

example, set the variable named

OMPI_MCA_btl_tcp_frag_size to the value 65536 (Bourne-style shells):

shell$ OMPI_MCA_btl_tcp_frag_size=65536

shell$ export OMPI_MCA_btl_tcp_frag_size

4. the mpirun command line:

--mca

Where is the name of the parameter.For

example:

shell$ mpirun --mca btl_tcp_frag_size 65536 -np 2 hello_world_mpi

These locations are checked in

order.For example, a parameter value passed on

the

mpirun command line will override an environment variable; an

environment

variable will override the system-wide defaults.