From 3789855545c6ce8c8493971d67af4b5cf50d9c6e Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Mon, 25 Mar 2024 14:21:35 -0700
Subject: [PATCH 1/5] `MultiFab::copy()`

Create a copy of this MultiFab, using the same Arena.
---
 Src/Base/AMReX_MultiFab.H   |  6 ++++++
 Src/Base/AMReX_MultiFab.cpp | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/Src/Base/AMReX_MultiFab.H b/Src/Base/AMReX_MultiFab.H
index b2fc9c80a1f..005a3dd154a 100644
--- a/Src/Base/AMReX_MultiFab.H
+++ b/Src/Base/AMReX_MultiFab.H
@@ -486,6 +486,12 @@ public:
                      int             dstcomp,
                      int             numcomp,
                      const IntVect&  nghost);
+
+
+    /** Create a copy of this MultiFab, using the same Arena.
+     */
+    MultiFab copy ();
+
     /**
     * \brief Copy from src to dst including nghost ghost cells.
     * The two MultiFabs MUST have the same underlying BoxArray.
diff --git a/Src/Base/AMReX_MultiFab.cpp b/Src/Base/AMReX_MultiFab.cpp
index 15f9490b1c2..072cbf074c5 100644
--- a/Src/Base/AMReX_MultiFab.cpp
+++ b/Src/Base/AMReX_MultiFab.cpp
@@ -167,6 +167,27 @@ MultiFab::Add (MultiFab& dst, const MultiFab& src,
     amrex::Add(dst, src, srccomp, dstcomp, numcomp, nghost);
 }
 
+MultiFab
+MultiFab::copy ()
+{
+    auto mf = MultiFab(
+        this->boxArray(),
+        this->DistributionMap(),
+        this->nComp(),
+        this->nGrowVect(),
+        MFInfo().SetArena(this->arena())
+    );
+    MultiFab::Copy(
+        mf,
+        *this,
+        0,
+        0,
+        this->nComp(),
+        this->nGrowVect()
+    );
+    return mf;
+}
+
 void
 MultiFab::Copy (MultiFab& dst, const MultiFab& src,
                 int srccomp, int dstcomp, int numcomp, int nghost)

From b7fdbf3d413c9a8324b3a12fe1a2a64218359bd8 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Mon, 25 Mar 2024 21:50:43 -0700
Subject: [PATCH 2/5] Conserve factory, too.

Co-authored-by: Weiqun Zhang <WeiqunZhang@lbl.gov>
---
 Src/Base/AMReX_MultiFab.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Src/Base/AMReX_MultiFab.cpp b/Src/Base/AMReX_MultiFab.cpp
index 072cbf074c5..6e61ee82999 100644
--- a/Src/Base/AMReX_MultiFab.cpp
+++ b/Src/Base/AMReX_MultiFab.cpp
@@ -175,7 +175,8 @@ MultiFab::copy ()
         this->DistributionMap(),
         this->nComp(),
         this->nGrowVect(),
-        MFInfo().SetArena(this->arena())
+        MFInfo().SetArena(this->arena()),
+        this->Factory()
     );
     MultiFab::Copy(
         mf,

From 5cd477f3f4e13f9d00262c37f9520acdf33c0306 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Mon, 25 Mar 2024 22:13:21 -0700
Subject: [PATCH 3/5] Keep `FabArray<FArrayBox>::copy` Overloads

---
 Src/Base/AMReX_MultiFab.H | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Src/Base/AMReX_MultiFab.H b/Src/Base/AMReX_MultiFab.H
index 005a3dd154a..a149e2930fd 100644
--- a/Src/Base/AMReX_MultiFab.H
+++ b/Src/Base/AMReX_MultiFab.H
@@ -488,6 +488,8 @@ public:
                      const IntVect&  nghost);
 
 
+    using FabArray<FArrayBox>::copy;
+
     /** Create a copy of this MultiFab, using the same Arena.
      */
     MultiFab copy ();

From a1686f357772704ffeff9fce6cdc8cd8c2b31638 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Wed, 27 Mar 2024 15:09:39 -0700
Subject: [PATCH 4/5] Rename: `deepCopy`

---
 Src/Base/AMReX_MultiFab.H   | 10 +++++-----
 Src/Base/AMReX_MultiFab.cpp |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Src/Base/AMReX_MultiFab.H b/Src/Base/AMReX_MultiFab.H
index a149e2930fd..6cb4c46e7df 100644
--- a/Src/Base/AMReX_MultiFab.H
+++ b/Src/Base/AMReX_MultiFab.H
@@ -487,12 +487,12 @@ public:
                      int             numcomp,
                      const IntVect&  nghost);
 
-
-    using FabArray<FArrayBox>::copy;
-
-    /** Create a copy of this MultiFab, using the same Arena.
+    /** Create a deep copy of this MultiFab and its data.
+     *
+     * This uses the same arena and factory in the copy and copies
+     * all data.
      */
-    MultiFab copy ();
+    MultiFab deepCopy ();
 
     /**
     * \brief Copy from src to dst including nghost ghost cells.
diff --git a/Src/Base/AMReX_MultiFab.cpp b/Src/Base/AMReX_MultiFab.cpp
index 6e61ee82999..41ec0093b62 100644
--- a/Src/Base/AMReX_MultiFab.cpp
+++ b/Src/Base/AMReX_MultiFab.cpp
@@ -168,7 +168,7 @@ MultiFab::Add (MultiFab& dst, const MultiFab& src,
 }
 
 MultiFab
-MultiFab::copy ()
+MultiFab::deepCopy ()
 {
     auto mf = MultiFab(
         this->boxArray(),

From db8a619f517f18d6efdfd25cc7758cbab757f39c Mon Sep 17 00:00:00 2001
From: Weiqun Zhang <WeiqunZhang@lbl.gov>
Date: Wed, 27 Mar 2024 18:36:55 -0700
Subject: [PATCH 5/5] Apply suggestions from code review

---
 Src/Base/AMReX_MultiFab.H   | 2 +-
 Src/Base/AMReX_MultiFab.cpp | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Src/Base/AMReX_MultiFab.H b/Src/Base/AMReX_MultiFab.H
index 6cb4c46e7df..8ec62700cc1 100644
--- a/Src/Base/AMReX_MultiFab.H
+++ b/Src/Base/AMReX_MultiFab.H
@@ -492,7 +492,7 @@ public:
      * This uses the same arena and factory in the copy and copies
      * all data.
      */
-    MultiFab deepCopy ();
+    [[nodiscard]] MultiFab deepCopy () const;
 
     /**
     * \brief Copy from src to dst including nghost ghost cells.
diff --git a/Src/Base/AMReX_MultiFab.cpp b/Src/Base/AMReX_MultiFab.cpp
index 41ec0093b62..2a80123836b 100644
--- a/Src/Base/AMReX_MultiFab.cpp
+++ b/Src/Base/AMReX_MultiFab.cpp
@@ -168,9 +168,9 @@ MultiFab::Add (MultiFab& dst, const MultiFab& src,
 }
 
 MultiFab
-MultiFab::deepCopy ()
+MultiFab::deepCopy () const
 {
-    auto mf = MultiFab(
+    MultiFab mf(
         this->boxArray(),
         this->DistributionMap(),
         this->nComp(),