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Hello World

A minimal DMR application that prints the current process count after each reconfiguration.

Source: examples/hello-world/ in the DMR repository.

What it does​

  1. Initialises MPI and DMR.
  2. Registers the round policy.
  3. Calls dmr_check each iteration and prints rank/size.
  4. Exits cleanly after the configured number of iterations.

Running it​

cd examples/hello-world
cmake -B build && cmake --build build

DMR_DEFAULT_POLICY_MIN=2 DMR_DEFAULT_POLICY_MAX=4 \
dmr mpirun -n 2 ./hello-world

Expected output:

[rank 0 / 2] iteration 0
[rank 1 / 2] iteration 0
-- reconfiguration: 2 -> 4 nodes --
[rank 0 / 4] iteration 1
[rank 1 / 4] iteration 1
[rank 2 / 4] iteration 1
[rank 3 / 4] iteration 1

Key points​

  • restart_func just prints the new size, no data to redistribute in this toy example.
  • finalize_func is a no-op because no heap memory is allocated per-rank.