From e57d5dda6b5e5c5ddb956197dba7f1772b96fe5b Mon Sep 17 00:00:00 2001
From: Eden Rochman <ayudaparatodos98@gmail.com>
Date: Fri, 5 Jun 2026 08:28:22 +0200
Subject: [PATCH] Add n_collision to MPI SourceSite type

The MPI datatype must include all fields in the struct so that
collision count is transferred correctly between MPI ranks.
---
 src/initialize.cpp | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/initialize.cpp b/src/initialize.cpp
index 78b414f786..cd3df20dec 100644
--- a/src/initialize.cpp
+++ b/src/initialize.cpp
@@ -161,7 +161,7 @@ void initialize_mpi(MPI_Comm intracomm)
 
   // Create bank datatype
   SourceSite b;
-  MPI_Aint disp[14];
+  MPI_Aint disp[15];
   MPI_Get_address(&b.r, &disp[0]);
   MPI_Get_address(&b.u, &disp[1]);
   MPI_Get_address(&b.E, &disp[2]);
@@ -176,12 +176,13 @@ void initialize_mpi(MPI_Comm intracomm)
   MPI_Get_address(&b.wgt_born, &disp[11]);
   MPI_Get_address(&b.wgt_ww_born, &disp[12]);
   MPI_Get_address(&b.n_split, &disp[13]);
-  for (int i = 13; i >= 0; --i) {
+  MPI_Get_address(&b.n_collision, &disp[14]);
+  for (int i = 14; i >= 0; --i) {
     disp[i] -= disp[0];
   }
 
   // Block counts for each field
-  int blocks[] = {3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
+  int blocks[] = {3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1};
 
   // Types for each field
   MPI_Datatype types[] = {
@@ -198,10 +199,11 @@ void initialize_mpi(MPI_Comm intracomm)
     MPI_INT64_T, // progeny_id
     MPI_DOUBLE,  // wgt_born
     MPI_DOUBLE,  // wgt_ww_born
-    MPI_INT64_T  // n_split
+    MPI_INT64_T, // n_split
+    MPI_INT      // n_collision
   };
 
-  MPI_Type_create_struct(14, blocks, disp, types, &mpi::source_site);
+  MPI_Type_create_struct(15, blocks, disp, types, &mpi::source_site);
   MPI_Type_commit(&mpi::source_site);
 
   CollisionTrackSite bc;