From 6dce84a18c118e10df579b651400a26c09ce3929 Mon Sep 17 00:00:00 2001
From: Mike Jarvis <michael@jarvis.net>
Date: Tue, 18 Jul 2023 08:59:19 -0400
Subject: [PATCH] Copy target back to CPU in SubtractDelta

---
 src/Silicon.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/Silicon.cpp b/src/Silicon.cpp
index e778a69e12..2d38a16200 100644
--- a/src/Silicon.cpp
+++ b/src/Silicon.cpp
@@ -1278,6 +1278,12 @@ namespace galsim {
         // add=false
         // subtract_delta=false
         _addDelta<false, false>(target, _delta);
+
+        // And if doing this on the GPU, we need to copy back to the CPU now.
+#ifdef GALSIM_USE_GPU
+        T* targetData = static_cast<T*>(_targetData);
+#pragma omp target update from(targetData[0:_targetDataLength])
+#endif
     }
 
     template <typename T>