ParallelIOTests: Ensure that all ranks share the same RNG seed

franzpoeschel · franzpoeschel · commit d8a9f977d836 · 2026-02-03T18:59:16.000+01:00
Catch2 v3 randomizes the execution order
diff --git a/test/CatchRunner.cpp b/test/CatchRunner.cpp
@@ -28,6 +28,9 @@ int main(int argc, char *argv[])
     MPI_Init(&argc, &argv);
 
     Catch::Session session;
+    // session.configData().runOrder = Catch::TestRunOrder::Declared;
+    MPI_Bcast(
+        &session.configData().rngSeed, 1, MPI_UINT32_T, 0, MPI_COMM_WORLD);
     int result = session.applyCommandLine(argc, argv);
     if (result == 0)
     {

Original file line number	Diff line number	Diff line change
`@@ -28,6 +28,9 @@ int main(int argc, char *argv[])`
`28`	`28`	`MPI_Init(&argc, &argv);`
`29`	`29`
`30`	`30`	`Catch::Session session;`
	`31`	`+ // session.configData().runOrder = Catch::TestRunOrder::Declared;`
	`32`	`+ MPI_Bcast(`
	`33`	`+ &session.configData().rngSeed, 1, MPI_UINT32_T, 0, MPI_COMM_WORLD);`
`31`	`34`	`int result = session.applyCommandLine(argc, argv);`
`32`	`35`	`if (result == 0)`
`33`	`36`	`{`