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GPI-2
http://www.gpi-site.com
******************************************************************************
1. INTRODUCTION
===============
GPI-2 is the second generation of GPI (www.gpi-site.com). GPI-2
implements the GASPI specification (www.gaspi.de), an API
specification which originates from the ideas and concepts of GPI.
GPI-2 is an API for asynchronous communication. It provides a
flexible, scalable and fault tolerant interface for parallel
applications.
2. INSTALLATION
===============
Requirements:
-------------
The current version of GPI-2 has the following requirements.
Software:
- libibverbs v1.1.6 (Verbs library from OFED) if running on Infiniband.
- ssh server running on compute nodes (requiring no password).
The easiest way to install GPI-2 is by using the install.sh
script. The default settings install GPI-2 under /opt/GPI2/. This
location can be easily modified by passing the location with the -p
option to the install script.
For example,
./install.sh -p /prog/GPI2
installs GPI-2 under /prog/GPI2 instead of under the default location.
Infiniband support (default)
----------------------------
GPI-2 requires the libibverbs from the OFED stack. You can pass the
path of your OFED installation to the install script using the option
(--with-infiniband) for that, in case the install script is not able to find it:
You can see the install script usage:
./install.sh -h
Ethernet support
----------------
To install GPI-2 on a system without Infiniband, you can use the
option --with-ethernet. With this option standard TCP sockets are
used.
Such support is primarily targetted at the development of GPI-2
applications without the need to access a system with Infiniband, with
less focus on performance.
MPI Interoperability
--------------------
If you plan to use GPI-2 with MPI to, for instance, start an
incremental port of a large application or to use some libraries that
require MPI, you can enable MPI interoperability with the option:
./install.sh --with-mpi<=path_to_mpi_installation>
If you don't provide a path to your MPI installation and mpirun is in
your PATH, the installation script will take that MPI installation.
This will enable you to use GPI-2 with MPI where the only constraint
is that MPI_Init() must be invoked before gaspi_proc_init(). For this
MPI+GPI2 mixed mode, it is assumed that you start the application with
mpirun (or mpiexec, etc.).
Note that this option will build GPI-2 with MPI, requiring you to link
the MPI library to your GPI-2 application (even if you are not using
MPI). If you are interested in using GPI-2 only, do not build GPI-2
with this option.
You can build GPI-2 on your own. There are the following make targets:
all - Build everything
gpi - Build the GPI-2 library (including debug version)
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mic - Build the GPI-2 library for the MIC
tests - Build provided tests
docs - Generate documentation (requires doxygen)
clean - Clean-up
4. BUILDING GPI-2 APPLICATIONS
==============================
GPI-2 provides two libraries: libGPI2.a and libGPI2-dbg.a.
The libGPI2.a aims at high-performance and is to be used in production
whereas the libGPI2-dbg.a provides a debug version, with extra
parameter checking and debug messages and is to be used to debug and
during development.
5. RUNNING GPI-2 APPLICATIONS
=============================
The gaspi_run utility is used to start and run GPI-2
applications. A machine file with the hostnames of nodes where the
application will run, must be provided.
For example, to start 1 process per node (on 4 nodes), the machine
file looks like:
node01
node02
node03
node04
Similarly, to start 2 processes per node (on 4 nodes):
node01
node01
node02
node02
node03
node03
node04
node04
The gaspi_run utility is invoked as follows:
gaspi_run -m <machinefile> [OPTIONS] <path GASPI program>
IMPORTANT: The path to the program must exist on all nodes where the
program should be started.
The gaspi_run utility has the following further options [OPTIONS]:
-b <binary file> Use a different binary for first node (master).
The master (first entry in the machine file) is
started with a different application than the rest
of the nodes (workers).
-N Enable NUMA for processes on same node. With this
option it is only possible to start the same number
of processes as NUMA nodes present on the system.
The processes running on same node will be set with
affinity to the proper NUMA node.
-n <procs> Start as many <procs> from machine file.
This option is used to start less processes than
those listed in the machine file.
-d Run with GDB (debugger) on master node. With this
option, GDB is started in the master node, to allow
debugging the application.
-p Ping hosts before starting the binary to make sure
they are available.
-h Show help.
5. THE GASPI_LOGGER
===================
The gaspi_logger utility is used to view and separate the output from
all nodes when the function gaspi_printf is called. The gaspi_logger
is started, on another session, on the master node. The output of the
application, when using gaspi_printf, will be redirected to the
gaspi_logger. Other I/O routines (e.g. printf) will not.
A further separation of output (useful for debugging) can be achieved
by using the routine gaspi_printf_to which sends the output to the
gaspi_logger started on a particular node. For example,
gaspi_printf_to(1, "Hello 1\n");
will display the string "Hello 1" in the gaspi_logger started on rank
6. GPI-2 WITH CO-PROCESSOR (INTEL XEON PHI)
==========================================
GPI-2 can be used with the Intel Xeon Phi (MIC) where the MIC is used
as one node (running possibly more than one GPI-2 process).
To use GPI-2 on the MIC, you need to compile it using the Intel
compiler with the -mmic option. The Makefile includes a build target
mic for that end but this build target is not used by the installation
script. After successful compilation, GPI-2 for the MIC can be found
under lib64/mic. If you are having problems with the compilation, make
sure the OFED_PATH and OFED_MIC_PATH in src/make.inc is setup correctly.
Assuming that the MIC(s) is set up properly, GPI-2 requires:
- ssh connectivity (requiring no password)
- grouping of local host and MIC(s) by using the tool micctrl
micctrl --initdefaults
micctrl --addbridge=br0 --type=internal --ip=172.31.1.254
micctrl --network=static --bridge=br0 --ip=172.31.1.1
where for instance, mic0: 172.31.1.1, mic1: 172.31.1.2 etc.
The MIC must be visible to the whole cluster network. For instance,
if your cluster network is 192.168.1.0 on eth0 and you want to map
mic0 to 192.168.1.100 do:
iptables -t nat -A PREROUTING -d 192.168.1.100 -i eth0 -j DNAT --to-destination 172.31.1.1
iptables -t nat -A POSTROUTING -s 172.31.1.1 -o eth0 -j SNAT --to-source 192.168.1.100
After setup, the MIC hostname can simply be added to the machinefile
and be used as another host.
8. TROUBLESHOOTING AND KNOWN ISSUES
===================================
If you're having troubles when building GPI-2 with support for
Infiniband, make sure you have the OFED stack correctly installed and
running. You can change the OFED path in the definitions file make.inc
in the source directory (src) to the fix path in your system.
Rui Machado
committed
When installing GPI-2 with MPI mixed-mode support (using the option
--with-mpi<=path_to_mpi_installation>) and the installation is failing
when trying to build the tests due to missing libraries, you can
provide extra paths through available variables and be able to find
the missing paths. These are: GPI2_EXTRA_CFLAGS, GPI2_EXTRA_LIBS_PATH,
GPI2_EXTRA_LIBS.
For example:
GPI2_EXTRA_LIBS=-lmpl ./install.sh --with-mpi -p /opt/GPI2
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Environment variables
---------------------
You might have some trouble when your application requires some
dynamically set environment setting (e.g. the LD_LIBRARY_PATH), for
instance, through the module system of your jobs batch
system. Currently, neither the gaspi_run or the GPI-2 library take
care of such environment settings. To this situation there are 2
workarounds:
i) you set the required environment variables in your shell
initialization file (e.g. ~/.bashrc).
ii) you create an executable shell script which sets the required
environment variables and then starts the application. Then you can
use gaspi_run to start the application, providing the shell script as
the application to execute.
gaspi_run -m machinefile ./my_wrapper_script.sh
where my_wrapper_script.sh contains:
#!/bin/sh
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:<path_to_my_lib>
<path_to_my_application>/my_application <my_app_args>
exit $?
If you're running in MPI mixed-mode, starting your application with
mpirun/mpiexec, this should not be an issue.
=====================
GPI-2 is on-going work and more features are still to come. Here are
some that are in our roadmap:
- support to add spare nodes (fault tolerance)
- better debugging possibilities
For more information, check the GPI-2 website ( www.gpi-site.com ) and
don't forget to subscribe to the GPI-2 mailing list. You subscribe it
at https://listserv.itwm.fraunhofer.de/mailman/listinfo/gpi2-users