From 464f50cdb1039948f4324cfec0fe3539a2f09741 Mon Sep 17 00:00:00 2001
From: Eduard Valeyev <eduard@valeyev.net>
Date: Sun, 15 Mar 2026 11:08:56 -0400
Subject: [PATCH] foreach_inplace(A,B) needs to fence on entry and exit

---
 src/TiledArray/conversions/foreach.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/TiledArray/conversions/foreach.h b/src/TiledArray/conversions/foreach.h
index 2c77c91a0f..9129d4b321 100644
--- a/src/TiledArray/conversions/foreach.h
+++ b/src/TiledArray/conversions/foreach.h
@@ -692,6 +692,10 @@ inline std::enable_if_t<!is_dense_v<Policy>, void> foreach_inplace(
   // Set the arg with the new array
   left = detail::foreach<true, Op, LeftTile, LeftTile, Policy, RightTile>(
       std::forward<Op>(op), shape_reduction, left, right);
+
+  // must also fence after to prevent remote ranks start work on unprocessed
+  // tiles
+  if (fence) left.world().gop.fence();
 }
 
 /// @}