From 0ba7fed1faafbbd394399137bf210c7d2edda36c Mon Sep 17 00:00:00 2001
From: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>
Date: Wed, 31 Jul 2024 02:48:43 -0400
Subject: [PATCH] fix:fix LAMMPS MPI tests with mpi4py 4.0.0 (#4032)

The previous code works with mpi4py<4 but fails with mpi4py 4.0.0. I
don't know what breaking change was made.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Optimized potential energy calculation in the LAMMPS simulation by
restricting evaluation to the master process, reducing unnecessary
computations.

- **Chores**
- Improved control flow for better performance in parallel execution
contexts.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: Jinzhe Zeng <jinzhe.zeng@rutgers.edu>
(cherry picked from commit 1e7223666d58fca7ae131b0415706ccaf69a4f08)
---
 source/lmp/tests/run_mpi_pair_deepmd.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/lmp/tests/run_mpi_pair_deepmd.py b/source/lmp/tests/run_mpi_pair_deepmd.py
index b27774ce11..0c4291ab3a 100644
--- a/source/lmp/tests/run_mpi_pair_deepmd.py
+++ b/source/lmp/tests/run_mpi_pair_deepmd.py
@@ -54,8 +54,8 @@
 )
 lammps.pair_coeff("* *")
 lammps.run(0)
-pe = lammps.eval("pe")
 if rank == 0:
+    pe = lammps.eval("pe")
     arr = [pe]
     np.savetxt(output, np.array(arr))
 MPI.Finalize()