From c8e020e2fd5f0cdf6b240b771ad284864e222e08 Mon Sep 17 00:00:00 2001
From: Roland Haas <rhaas@illinois.edu>
Date: Wed, 8 Nov 2023 15:08:17 -0600
Subject: [PATCH 1/2] CarpetX: register dummy "CarpetX" interpoaltor with
 Cactus

this allows user code to use "CarpetX" when requesting an interpolator
handle
---
 CarpetX/src/driver.cxx      |  5 +++++
 CarpetX/src/interp.hxx      | 20 ++++++++++++++++++++
 CarpetX/src/interpolate.cxx | 28 ++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/CarpetX/src/driver.cxx b/CarpetX/src/driver.cxx
index 126af6ec3..c6536621c 100644
--- a/CarpetX/src/driver.cxx
+++ b/CarpetX/src/driver.cxx
@@ -2301,6 +2301,11 @@ extern "C" int CarpetX_Startup() {
   CCTK_OverloadInterpGridArrays(CarpetX_InterpGridArrays);
   CCTK_OverloadArrayGroupSizeB(ArrayGroupSizeB);
   CCTK_OverloadGroupDynamicData(GroupDynamicData);
+
+  iret = CCTK_InterpRegisterOpLocalUniform(InterpLocalUniform, "CarpetX",
+                                           CCTK_THORNSTRING);
+  assert(!iret && "CCTK_InterpRegisterOpLocalUniform failed");
+
   return 0;
 }
 
diff --git a/CarpetX/src/interp.hxx b/CarpetX/src/interp.hxx
index 906de0991..6eca375a9 100644
--- a/CarpetX/src/interp.hxx
+++ b/CarpetX/src/interp.hxx
@@ -22,4 +22,24 @@ extern "C" CCTK_INT CarpetX_DriverInterpolate(
     CCTK_INT const N_output_arrays, CCTK_INT const output_array_type_codes[],
     CCTK_POINTER const output_arrays[]);
 
+namespace CarpetX {
+// a dummy routine for now
+// TODO: implement this for actual local interpolation
+int InterpLocalUniform(int N_dims, int param_table_handle,
+                       /***** coordinate system *****/
+                       const CCTK_REAL coord_origin[],
+                       const CCTK_REAL coord_delta[],
+                       /***** interpolation points *****/
+                       int N_interp_points, int interp_coords_type_code,
+                       const void *const interp_coords[],
+                       /***** input arrays *****/
+                       int N_input_arrays, const CCTK_INT input_array_dims[],
+                       const CCTK_INT input_array_type_codes[],
+                       const void *const input_arrays[],
+                       /***** output arrays *****/
+                       int N_output_arrays,
+                       const CCTK_INT output_array_type_codes[],
+                       void *const output_arrays[]);
+} // namespace CarpetX
+
 #endif // #ifndef CARPETX_CARPETX_INTERP_HXX
diff --git a/CarpetX/src/interpolate.cxx b/CarpetX/src/interpolate.cxx
index 0cdabbb08..df9ef5cd6 100644
--- a/CarpetX/src/interpolate.cxx
+++ b/CarpetX/src/interpolate.cxx
@@ -307,6 +307,25 @@ template <typename T, int order, int centering> struct interpolator {
 
 } // namespace
 
+int InterpLocalUniform(int /*N_dims*/, int /*param_table_handle*/,
+                       /***** coordinate system *****/
+                       const CCTK_REAL /*coord_origin*/[],
+                       const CCTK_REAL /*coord_delta*/[],
+                       /***** interpolation points *****/
+                       int /*N_interp_points*/, int /*interp_coords_type_code*/,
+                       const void *const /*interp_coords*/[],
+                       /***** input arrays *****/
+                       int /*N_input_arrays*/,
+                       const CCTK_INT /*input_array_dims*/[],
+                       const CCTK_INT /*input_array_type_codes*/[],
+                       const void *const /*input_arrays*/[],
+                       /***** output arrays *****/
+                       int /*N_output_arrays*/,
+                       const CCTK_INT /*output_array_type_codes*/[],
+                       void *const /*output_arrays*/[]) {
+  CCTK_ERROR("Dummy InterpLocalUniform function called");
+}
+
 extern "C" CCTK_INT CarpetX_InterpGridArrays(
     cGH const *const cctkGH, int const N_dims, int const local_interp_handle,
     int const param_table_handle, int const coord_system_handle,
@@ -342,6 +361,15 @@ extern "C" CCTK_INT CarpetX_DriverInterpolate(
     CCTK_POINTER const output_arrays[]) {
   DECLARE_CCTK_PARAMETERS;
 
+  // We do not support local interpolators yet
+  const int carpetx_interp_handle = CCTK_InterpHandle("CarpetX");
+  assert(carpetx_interp_handle >= 0);
+  if (carpetx_interp_handle != local_interp_handle) {
+    CCTK_VERROR("Incorrect local interpolator handle provided, only 'CarpetX' "
+                "is allowed: %d != %d",
+                local_interp_handle, carpetx_interp_handle);
+  }
+
   // This verifies that the order in param_table_handle matches the order of the
   // runtime parameter from CarpetX
   CCTK_INT order;

From 4914fd83ffcd83201bbd6c3693882331cfe6d9a2 Mon Sep 17 00:00:00 2001
From: Roland Haas <rhaas@illinois.edu>
Date: Fri, 10 Nov 2023 12:36:49 -0600
Subject: [PATCH 2/2] TestInterpolate: adapt to CarpetX's interpolator
 requiring a handle

---
 TestInterpolate/src/test_interpolation.cxx | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/TestInterpolate/src/test_interpolation.cxx b/TestInterpolate/src/test_interpolation.cxx
index 2516b6e60..54c32e214 100644
--- a/TestInterpolate/src/test_interpolation.cxx
+++ b/TestInterpolate/src/test_interpolation.cxx
@@ -99,7 +99,10 @@ extern "C" void TestInterpolate_test_interpolation(CCTK_ARGUMENTS) {
   CCTK_INT const coord_system_handle = 0;
   CCTK_INT const interp_coords_type_code = 0;
   CCTK_INT const output_array_type_codes[1] = {0};
-  int interp_handle = 0;
+  int interp_handle = CCTK_InterpHandle("CarpetX");
+
+  if(interp_handle < 0)
+    CCTK_VERROR("Could not obtain inteprolator handle for built-in 'CarpetX' interpolator: %d", interp_handle);
 
   /* Table generation */
   int operands[DIM(all_operations)][DIM(all_varinds)];