Compiling Software for OSG Connect¶
Compiling Software for OSG Connect¶
Due to the distributed nature of the Open Science Pool, you will always need to ensure that your jobs have access to the software that will be executed. This guide provides useful information for compiling and using your software in OSG Connect. A detailed example of performing software compilation is additionally available at OSG Connect Example Compilation Guide.
What is compiling? The process of compiling converts human readable code into binary, machine readable code that will execute the steps of the program.
Get software source code¶
The first step to compiling your software is to locate and download the source code, being sure to select the version that you want. Source code will often be made available as a compressed tar archive which will need to be extracted for before compilation.
You should also carefully review the installation instructions provided by the software developers. The installation instructions should include important information regarding various options for configuring and performing the compilation. Also carefully note any system dependencies (hardware, other software, and libraries) that are required for your software.
Select the appropriate compiler and compilation options¶
A compiler is a program that is used to peform source code compilation. The GNU Compiler
Collection (GCC) is a common, open source collection of compilers with support for C, C++,
fotran, and other languages, and includes important libraries for supporting your compilation
and sometimes software execution. Your software compilation may require certain versions
of a compiler which should be noted in the installation instructions or system dependencies
documention. Currently the login nodes have
GCC 4.8.5 as the default version, but newer
versions of GCC may also be available - to learn more please contact firstname.lastname@example.org.
Static versus dynamic linking during compilation¶
Binary code often depends on additional information (i.e. instructions) from other software, known as libraries, for proper execution. The default behavior when compiling, is for the final binary to be "dynamically linked" to libraries that it depends on, such that when the binary is executed, it will look for these library files on the system that it is running on. Thus a copy of the appropriate library files will need to be available to your software wherever it runs. OSG Connect users can transfer a copy of the necessary libraries along with with their jobs to manage such dependencies if not supported by the execute node that your jobs run on.
However, the option exists to "statically link" the library dependencies of your software. By statically linking libraries during compilation, the library code will be directly packaged with your software binary meaning the libraries will always be available to your software which your software to run on more execute nodes.
To statically link libraries during compilation, use the
-static flag when running
--enable-static when running a
configure script, or set your
environment variable to
Get access to libraries needed for your software¶
As described above, your software may require additional software, known as libraries, for
compilation and execution. For greatest portability of your software, we recommend installing
the libraries needed for your software and transferring a copy of the libraries along with
your subsequent jobs. When using libraries that you have installed yourself, you will likely
need to add these libraries to your
LIBRARY_PATH environment variable before compiling
your software. There may also be additional environment variables that will need to be
defined or modified for software compilation, this information should be provided
in the installtion instructions of your software. For any libraries added to
before software compilation, you'll also need to add these same libraries to
LD_LIBRARY_PATH as a step in your job's executable bash script before executing
Perform your compilation¶
Software compilation is easiest to perform interactively, and OSG Connect users are
welcome to compile software directly on their assigned login node. This will ensure
that your application is built on an environment that is similar to the majority
of the compute nodes on OSG. Because OSG Connect login nodes currently use the
Red Hat Enterprise Linux 7 operating system, your software will, generally, only be
compatible for execution on RHEL 7 or similar operating systems. You can use the
requirements statement of your HTCondor submit file to direct your jobs to execute
nodes with specific operating systems, for instance:
requirements = (OSGVO_OS_STRING == "RHEL 7")
Software installation typically includes three steps: 1.) configuration, 2.) compilation, and 3.) "installation" which places the compiled code in a specific location. In most cases, these steps will be achieved with the following commands:
./configure make make install
Most software is written to install to a default location, however your OSG Connect
account is not authorized to write to these default system locations. Instead, you will want to
create a folder for your software installation in your
home directory and use an option in the
configuration step that will install the software to this folder:
username should be replaced with your OSG Connect username and
path replaced with the
path to the directory you created for your software installation.
Watch out for hardware feature detection¶
Some software builds might try to optimize the software for the particular host you are building on. In general this is a good idea (optimized code will perform better), but be aware that not all execution endpoints on OSG are the same. If your software picks up hardware features such as AVX/AVX2, you might have to ensure the jobs are running on hardware with those features. For example, if your software requires AVX2:
requirements = (OSGVO_OS_STRING == "RHEL 7") && (HAS_AVX2 == True)
Please see Control Where Your Jobs Run / Job Requirements
Use Your Software¶
When submitting jobs, you will need to transfer a copy of your compiled software,
and any dynamically-linked dependencies that you also installed. Our
Introduction to Data Management on OSG Connect
guide is a good starting point for more information for selecting the appropriate
methods for transferring you software. Depending on your job workflow, it may be possible
to directly specify your executable binary as the
executable in your HTCondor
When using your software in subsequent job submissions, be sure to add additional
commands to the executable bash script to define evironment variables, like for instance
LD_LIBRARY_PATH, that may be needed to properly execute your software.
Get Additional Assistance¶
If you have questions or need assistance, please contact email@example.com.