Make sure fixed source resample is reproducible for MPI runs

src/simulation.F90

@@ -275,8 +275,8 @@ contains
       if (master .and. current_gen /= gen_per_batch) call print_generation()
     elseif (run_mode == MODE_FIXEDSOURCE) then
       ! For fixed-source mode, we need to sample the external source
-      call set_particle_seed(overall_gen*n_particles)
       do i = 1, work
+        call set_particle_seed(overall_gen*n_particles + work_index(rank) + i)
         call sample_external_source(source_bank(i))
       end do
     end if

tests/test_fixed_source/results_true.dat

@@ -1,6 +1,6 @@
 tally 1:
-4.460676E+02
-1.993197E+04
+4.448476E+02
+1.984373E+04
 leakage:
-9.660000E+00
-9.335800E+00
+9.790000E+00
+9.588300E+00

tests/test_particle_restart_fixed/results_true.dat

@@ -1,16 +1,16 @@
 current batch:
-9.000000E+00
+7.000000E+00
 current gen:
 1.000000E+00
 particle id:
-5.900000E+02
+1.440000E+02
 run mode:
 fixed source
 particle weight:
 1.000000E+00
 particle energy:
-5.284635E+00
+5.749729E+00
 particle xyz:
-4.995064E+00 7.895146E+00 1.198717E+00
+8.754675E+00 2.551620E+00 4.394350E-01
 particle uvw:
-7.594252E-01 3.731736E-01 -5.329305E-01
+-5.971721E-01 -4.845709E-01 6.391999E-01

tests/test_particle_restart_fixed/test_particle_restart_fixed.py

@@ -7,5 +7,5 @@ from testing_harness import ParticleRestartTestHarness
 
 
 if __name__ == '__main__':
-    harness = ParticleRestartTestHarness('particle_9_590.h5')
+    harness = ParticleRestartTestHarness('particle_7_144.h5')
     harness.main()