Checkpointing
This page describes how to use the checkpointing capability of MPICH.
Configuration
First, you need to have BLCR version 0.8.2 or later installed on your machine. If it's installed in the default system location, add the following two options to your configure command:
--enable-checkpointing --with-hydra-ckpointlib=blcr
If BLCR is not installed in the default system location, you'll need to tell MPICH's configure where to find it. You might also need to set the LD_LIBRARY_PATH environment variable so that BLCR's shared libraries can be found. In this case add the following options to your configure command:
--enable-checkpointing --with-hydra-ckpointlib=blcr --with-blcr=<BLCR_INSTALL_DIR> LD_LIBRARY_PATH=<BLCR_INSTALL_DIR>/lib
where <BLCR_INSTALL_DIR> is the directory where BLCR has been installed (whatever was specified in --prefix when BLCR was configured).
After it's configured compile as usual (e.g., make; make install).
Note, checkpointing is only supported with the Hydra process manager.
Verifying Checkpointing Support
Make sure MPICH is correctly configured with BLCR. You can do this using:
mpiexec -info
This should display 'BLCR' under 'Checkpointing libraries available'.
Checkpointing the Application
There are two ways to cause the application to checkpoint. You can ask mpiexec to periodically checkpoint the application using the mpiexec option -ckpoint-interval (seconds):
mpiexec -ckpointlib blcr -ckpoint-prefix /tmp/app.ckpoint \
-ckpoint-interval 3600 -f hosts -n 4 ./app
Alternatively, you can also manually force checkpointing by sending a SIGUSR1 signal to mpiexec.
The checkpoint/restart parameters can also be controlled with the environment variables HYDRA_CKPOINTLIB, HYDRA_CKPOINT_PREFIX and HYDRA_CKPOINT_INTERVAL.
To restart a process:
mpiexec -ckpointlib blcr -ckpoint-prefix /tmp/app.ckpoint -f hosts -n 4 -ckpoint-num <N>
where <N> is the checkpoint number you want to restart from.
Notes on the implementation of checkpointing on Nemesis can be found here.
