DLB is a dynamic library designed to speed up HPC hybrid applications (i.e., two levels of parallelism) by improving the load balance of the outer level of parallelism (e.g., MPI) by dynamically redistributing the computational resources at the inner level of parallelism (e.g., OpenMP). at run time.

This dynamism allows DLB to react to different sources of imbalance: Algorithm, data, hardware architecture and resource availability among others.

LeWI (Lend When Idle) is the algorithm used to redistribute the computational resources that are not being used from one process to another process inside the same shared memory node in order to speed up its execution.

DROM (Dynamic Resource Ownership Manager) is the algorithm used to manage the CPU affinity of a process running a shared memory programming model (e.g., OpenMP).

1. Build requirements

   • A supported platform running Linux (i386, x86-64, ARM, PowerPC or IA64)
   • GNU C/C++ compiler versions 4.4 or higher
   • Python 2.4 or higher

2. Download DLB code

   1. From a git repository

      • Clone DLB repository

        • From GitHub:

          git clone https://github.com/bsc-pm/dlb.git

        • From our internal GitLab repository (BSC users only):

          git clone https://pm.bsc.es/gitlab/dlb/dlb.git

      • Bootstrap autotools:

        cd dlb
        ./bootstrap

   2. From a distributed tarball
      • Download a tarball from DLB Downloads or GitHub releases

3. Run configure. Optionally, check the configure flags by running ./configure -h to see detailed information about some features.

   ./configure --prefix=<DLB_PREFIX> [<configure-flags>]

4. Build ans install

   make
   make install

5. Optionally, add the installed bin directory to your PATH

   export PATH=<DLB_PREFIX>/bin:$PATH

For more information about the autotools installation process, please refer to INSTALL

Simply link or preload a binary with the DLB shared library libdlb.so and configure DLB using the environment variable DLB_ARGS.

# Link application
mpicc -o myapp myapp.c -L<DLB_PREFIX>/lib -ldlb -Wl,-rpath,<DLB_PREFIX>/lib

# Launch two processes sharing resources
export LB_ARGS="--policy=lewi"
mpirun -n 2 ./myapp

# Launch an application preloading DLB
export OMP_NUM_THREADS=4
export LD_PRELOAD=<DLB_PREFIX>/lib/libdlb.so
taskset -c 0-3 ./myapp &

# Reduce CPU binding to [1,3] and threads to 2
myapp_pid=$!
dlb_taskset -p $myapp_pid -c 1,3

Please refer to our DLB User Guide for a more complete documentation.

If you want to cite DLB, you can use the following publications:

• Hints to improve automatic load balancing with LeWI for hybrid applications at Journal of Parallel and Distributed Computing 2014. (ScienceDirect) (bibtex) (pdf)

• LeWI: A Runtime Balancing Algorithm for Nested Parallelism at International Conference in Parallel Processing 2009, ICPP09. (IEEE Xplore) (bibtex) (pdf)

For questions, suggestions and bug reports, you can contact us via e-mail at [email protected].