From 89e3ce1b6f16e918476c249583c80660d98112bb Mon Sep 17 00:00:00 2001
From: Anders Johansson <anjohan@uio.no>
Date: Tue, 4 Jun 2024 11:58:29 -0400
Subject: [PATCH] attempt fix empty domains also in non-Kokkos pair and compute
 (#45), also force C++17 because of insert_or_assign. Compiles but untested.

---
 compute_allegro.cpp | 46 +++++++++++++++++++++++++++++----------------
 pair_allegro.cpp    |  3 +++
 patch_lammps.sh     |  2 +-
 3 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/compute_allegro.cpp b/compute_allegro.cpp
index f8738e7..ed350d3 100644
--- a/compute_allegro.cpp
+++ b/compute_allegro.cpp
@@ -101,18 +101,27 @@ void ComputeAllegro<peratom>::compute_vector()
 {
   invoked_vector = update->ntimestep;
 
-  const torch::Tensor &quantity_tensor =
-      ((PairAllegro<lowhigh> *) force->pair)->custom_output.at(quantity).cpu().ravel();
+  // empty domain, pair style won't store tensor
+  // note: assumes nlocal == inum
+  if (atom->nlocal == 0) {
+    for (int i = 0; i < size_vector; i++) {
+      vector[i] = 0.0;
+    }
+  } else {
+    const torch::Tensor &quantity_tensor =
+        ((PairAllegro<lowhigh> *) force->pair)->custom_output.at(quantity).cpu().ravel();
 
-  auto quantity = quantity_tensor.data_ptr<double>();
+    auto quantity = quantity_tensor.data_ptr<double>();
 
-  if (quantity_tensor.size(0) != size_vector) {
-    error->one(FLERR, "size {} of quantity tensor {} does not match expected {} on rank {}",
-               quantity_tensor.size(0), this->quantity, size_vector, comm->me);
-  }
+    if (quantity_tensor.size(0) != size_vector) {
+      error->one(FLERR, "size {} of quantity tensor {} does not match expected {} on rank {}",
+                 quantity_tensor.size(0), this->quantity, size_vector, comm->me);
+    }
 
-  for (int i = 0; i < size_vector; i++) { vector[i] = quantity[i]; }
+    for (int i = 0; i < size_vector; i++) { vector[i] = quantity[i]; }
+  }
 
+  // even if empty domain
   MPI_Allreduce(MPI_IN_PLACE, vector, size_vector, MPI_DOUBLE, MPI_SUM, world);
 }
 
@@ -128,18 +137,23 @@ void ComputeAllegro<peratom>::compute_peratom()
     if (nperatom==1) vector_atom = &array_atom[0][0];
   }
 
-  const torch::Tensor &quantity_tensor =
-      ((PairAllegro<lowhigh> *) force->pair)->custom_output.at(quantity).cpu().contiguous().reshape({-1,nperatom});
+  // guard against empty domain (pair style won't store tensor)
+  if (atom->nlocal > 0) {
+    const torch::Tensor &quantity_tensor =
+        ((PairAllegro<lowhigh> *) force->pair)->custom_output.at(quantity).cpu().contiguous().reshape({-1,nperatom});
 
-  auto quantity = quantity_tensor.accessor<double,2>();
-  quantityptr = quantity_tensor.data_ptr<double>();
+    auto quantity = quantity_tensor.accessor<double,2>();
+    quantityptr = quantity_tensor.data_ptr<double>();
 
-  int nlocal = atom->nlocal;
-  for (int i = 0; i < nlocal; i++) {
-    for (int j = 0; j < nperatom; j++) {
-      array_atom[i][j] = quantity[i][j];
+    int nlocal = atom->nlocal;
+    for (int i = 0; i < nlocal; i++) {
+      for (int j = 0; j < nperatom; j++) {
+        array_atom[i][j] = quantity[i][j];
+      }
     }
   }
+
+  // even if empty domain
   if (newton) comm->reverse_comm(this);
 }
 
diff --git a/pair_allegro.cpp b/pair_allegro.cpp
index 57e0354..f5e1360 100644
--- a/pair_allegro.cpp
+++ b/pair_allegro.cpp
@@ -335,6 +335,9 @@ template <Precision precision> void PairAllegro<precision>::compute(int eflag, i
   // Neighbor list per atom
   int **firstneigh = list->firstneigh;
 
+  // Skip calculation if empty domain
+  if (inum==0) return;
+
   // Total number of bonds (sum of number of neighbors)
   int nedges = 0;
 
diff --git a/patch_lammps.sh b/patch_lammps.sh
index dd66e31..f063478 100755
--- a/patch_lammps.sh
+++ b/patch_lammps.sh
@@ -68,7 +68,7 @@ fi
 
 echo "Updating CMakeLists.txt..."
 
-sed -i "s/set(CMAKE_CXX_STANDARD 11)/set(CMAKE_CXX_STANDARD 14)/" $lammps_dir/cmake/CMakeLists.txt
+sed -i "s/set(CMAKE_CXX_STANDARD 11)/set(CMAKE_CXX_STANDARD 17)/" $lammps_dir/cmake/CMakeLists.txt
 
 # Add libtorch
 cat >> $lammps_dir/cmake/CMakeLists.txt << "EOF2"