From e8dba2bec56646bb6e2a4b8f9c419da47cab662a Mon Sep 17 00:00:00 2001
From: Christopher Schwan <handgranaten-herbert@posteo.de>
Date: Tue, 6 Aug 2024 12:39:30 +0200
Subject: [PATCH] Fix bug in DIS evolution

---
 pineappl/src/evolution.rs | 2 +-
 pineappl/src/grid.rs      | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/pineappl/src/evolution.rs b/pineappl/src/evolution.rs
index 1bb7433e..d3f6a970 100644
--- a/pineappl/src/evolution.rs
+++ b/pineappl/src/evolution.rs
@@ -500,7 +500,7 @@ pub(crate) fn evolve_slice_with_one(
         }));
     }
 
-    let pid = grid.channels()[0].entry()[0].0[index];
+    let pid = grid.channels()[0].entry()[0].0[1 - index];
 
     Ok((
         Array1::from_iter(sub_fk_tables)
diff --git a/pineappl/src/grid.rs b/pineappl/src/grid.rs
index 4a997a03..baf2dfc4 100644
--- a/pineappl/src/grid.rs
+++ b/pineappl/src/grid.rs
@@ -1582,6 +1582,9 @@ impl Grid {
         // TODO: convert this unwrap into error
         let grid = lhs.unwrap();
 
+        // check that the convolutions are unchanged
+        assert_eq!(self.convolutions(), grid.convolutions());
+
         // UNWRAP: merging evolved slices should be a proper FkTable again
         Ok(FkTable::try_from(grid).unwrap_or_else(|_| unreachable!()))
     }