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title Quick start
nav_order 2
description Build MANA, run an example under MANA, checkpoint it and restart it.

Quick start

{: .no_toc }

This page builds MANA, runs an example program under MANA on one host, checkpoints it, and restarts it. It takes about ten minutes. {: .fs-6 .fw-300 }

  1. TOC {:toc}

Before you start

You need an MPI library with its compiler wrappers (mpicc, mpicxx and mpifort) in PATH, a C++20 compiler, and Python 3. On Debian and Ubuntu, also install the package libc6-dbg. Install gives the full list of requirements.

1. Build MANA

git clone https://github.com/mpickpt/mana
cd mana
./configure      # also checks out DMTCP, the dmtcp submodule of MANA
make -j8

make puts the MANA commands in bin/ and the libraries in lib/dmtcp/. Run the commands below from the top directory of MANA.

2. Build the example program

make -C examples

This builds examples/ring. In each step, the program passes a token around a ring of all ranks and sums one value per rank. It runs 60 steps of one second each, and rank 0 prints one line per step. The options -n STEPS and -s SECONDS change these values.

3. Start a coordinator

bin/mana_coordinator

The coordinator controls the checkpoints of a job. It runs in the background. It writes its host and port to ~/.mana.rc, where the other MANA commands find them.

4. Run the program under MANA

mpirun -np 4 bin/mana_launch examples/ring

mana_launch runs each rank under MANA. Give mana_launch to the MPI launcher in place of the program, and give the program to mana_launch.

5. Checkpoint the job

While the job runs, open another shell in the same directory, and type:

bin/mana_status --checkpoint

Each rank N writes its checkpoint into the directory ckpt_rank_N in the current directory. Then the job continues.

6. Stop the job

Stop the job with Ctrl-C in the first shell.

7. Restart the job

A coordinator stops when the last rank of its job stops. So, start a new coordinator, and then restart the job:

bin/mana_coordinator
mpirun -np 4 bin/mana_restart

The job continues from the step of the checkpoint, not from step 1. Restart with the same number of ranks as the original job.

{: .note } mana_launch does not start if the checkpoint directory already contains ckpt_rank_* directories. Move or delete an old checkpoint before you launch a new job. make tidy deletes the checkpoints in the top directory of MANA.

On a cluster with Slurm

Use the same commands in an allocation, and use srun in place of mpirun:

salloc -N 2 -t 01:00:00
bin/mana_coordinator
srun -N 2 bin/mana_launch examples/ring

Clusters and Slurm gives more information.

Next steps