Updated 2021-05-17

Run Cap’n Proto C++ on the Cluster


  • Cap'n Proto C++ is a fast data interchange format and RPC system
  • Use module avail capnproto to see all the available versions on the cluster. Currently, on RHEL6, only capnproto-c++/0.5.3 is available
  • To load Cap'n Proto in your PBS script:
    • Load its dependent module first with module load gcc/4.9.0
    • Load Cap'n Proto with module load capnproto-c++/0.5.3
  • To run Cap'n Proto:
    • In your PBS script, put all lines executing Cap'n Proto after the module load line.
    • Example: capnp decode myschema.capnp MyType < message.bin > message.txt would go in the PBS script after the lines that load the correct modules for Cap'n Proto

Example PBS Script

#PBS -N capnprotoTest
#PBS -A [Account] 
#PBS -l nodes=2:ppn=4
#PBS -l walltime=20:00
#PBS -q inferno
#PBS -j oe
#PBS -o capnprotoResult.out

module load gcc/4.9.0
module load capnproto-c++/0.5.3
capnp decode myschema.capnp MyType < message.bin > message.txt
  • The #PBS directives are standard, requesting 20 min of walltime and 2 nodes with 4 cores per node. More on #PBS directives can be found in the PBS guide


If using $PBS_O_WORKDIR, the .capnp file, as well as any other files required for the job, must be stored in the same folder as the PBS script

  • $PBS_O_WORKDIR is simply a variable that represents the directory you submit the PBS script from. Make sure the .capnp files, and any other files you need are in the same directory you put the PBS script in. This line tells the cluster to enter this directory where you have stored the PBS script, and look for all the files for the job. If you use $PBS_O_WORKDIR, you need to have all your files in the same folder as your PBS script otherwise the cluster won't be able to find the files it needs.
  • The module load lines load Cap'n Proto and its dependent module (gcc)
  • The capnp decode line is just a general example showing how Cap'n Proto might be used, and is taken from the Cap'n Proto Documentation. Check out the documentation for much more info on Cap'n Proto's functionality.
  • The point of the capnp decode line is to show that commands executing the program must be included after:
    • Entering the correct folder with all the files and PBS script, in this case achieved with cd $PBS_O_WORKDIR
    • Cap'n Proto is loaded with the module load lines

Submit Job and Check Status

  • Make sure you're in the directory that contains the PBS script, the .capnp file, and any other files you need.
  • Submit with qsub <pbs script name>. In this case qsub capnproto.pbs or whatever you called the PBS script. You can name the PBS scripts whatever you want, just keep the .pbs at the end
  • Check job status with qstat -u username3 -n, replacing "username3" with your gt username
  • You can delete the job with qdel 22182721, replacing the number with the jobid returned after running qsub
  • Depending on the resources requested and queue the job is run on, it may take varying amounts of time for the job to start. To estimate the time until the job executes, run showstart 22182721, replacing the number with the jobid returned after running qsub. More helpful commands can be found in this guide

Collecting Results

  • All files created will be in the same folder where your PBS script is (same directory you ran qsub from)
  • The .out file will be found here as well. It contains the results of the job, as well as diagnostics and a report of resources used during the job. If the job fails or doesn't produce the result your were hoping for, the .out file is a great debugging tool.
  • You can transfer the resulting files off the cluster using scp or a file transfer service