From 9cb7bba27aebd116eafefa2296d5aab92d356f85 Mon Sep 17 00:00:00 2001
From: Steven Roberts <roberts115@llnl.gov>
Date: Tue, 30 Jul 2024 21:49:21 -0700
Subject: [PATCH] Start adaptivity unit test

---
 .../unit_tests/arkode/C_serial/CMakeLists.txt |   1 +
 .../arkode/C_serial/ark_test_adapt.c          | 122 ++++++++++++++++++
 2 files changed, 123 insertions(+)
 create mode 100644 test/unit_tests/arkode/C_serial/ark_test_adapt.c

diff --git a/test/unit_tests/arkode/C_serial/CMakeLists.txt b/test/unit_tests/arkode/C_serial/CMakeLists.txt
index 6794a213b4..3670b76da4 100644
--- a/test/unit_tests/arkode/C_serial/CMakeLists.txt
+++ b/test/unit_tests/arkode/C_serial/CMakeLists.txt
@@ -16,6 +16,7 @@
 
 # List of test tuples of the form "name\;args"
 set(ARKODE_unit_tests
+    "ark_test_adapt\;"
     "ark_test_arkstepsetforcing\;1 0"
     "ark_test_arkstepsetforcing\;1 1"
     "ark_test_arkstepsetforcing\;1 2"
diff --git a/test/unit_tests/arkode/C_serial/ark_test_adapt.c b/test/unit_tests/arkode/C_serial/ark_test_adapt.c
new file mode 100644
index 0000000000..4e98e2fe4b
--- /dev/null
+++ b/test/unit_tests/arkode/C_serial/ark_test_adapt.c
@@ -0,0 +1,122 @@
+/* -----------------------------------------------------------------------------
+ * Programmer(s): Steven B. Roberts @ LLNL
+ * -----------------------------------------------------------------------------
+ * SUNDIALS Copyright Start
+ * Copyright (c) 2002-2024, Lawrence Livermore National Security
+ * and Southern Methodist University.
+ * All rights reserved.
+ *
+ * See the top-level LICENSE and NOTICE files for details.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SUNDIALS Copyright End
+ * -----------------------------------------------------------------------------
+ * Unit test for GetUserData functions
+ * ---------------------------------------------------------------------------*/
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "arkode/arkode_erkstep.h"
+#include "nvector/nvector_serial.h"
+
+static void err_fn(int line, const char* func, const char* file, const char* msg,
+                   SUNErrCode err_code, void* err_user_data, SUNContext sunctx)
+{
+  fprintf(stderr, "Error at line %i of %s in %s: %s\n", line, func, file, msg);
+  exit(err_code);
+}
+
+static int f(sunrealtype t, N_Vector y, N_Vector ydot, void* user_data)
+{
+  N_VConst(SUN_RCONST(0.0), ydot);
+  return 0;
+}
+
+static int check_step(void* arkode_mem, N_Vector y, sunrealtype h_expected)
+{
+  static int step = 0;
+  step++;
+
+  sunrealtype tret;
+  ARKodeEvolve(arkode_mem, SUN_RCONST(1.0), y, &tret, ARK_ONE_STEP);
+
+  long int local_err_fails;
+  ARKodeGetNumErrTestFails(arkode_mem, &local_err_fails);
+  if (local_err_fails != 0)
+  {
+    fprintf(stderr, "Expected 0 local error failures at step %i but is %li\n",
+            step, local_err_fails);
+  }
+
+  const N_Vector err = N_VClone(y);
+  ARKodeGetEstLocalErrors(arkode_mem, err);
+  sunrealtype err_norm = N_VMaxNorm(err);
+  N_VDestroy(err);
+
+  if (err_norm != 0)
+  {
+    fprintf(stderr, "Expected local error at step %i to be 0 but is %g\n", step,
+            err_norm);
+    return 1;
+  }
+
+  sunrealtype h_actual;
+  ARKodeGetCurrentStep(arkode_mem, &h_actual);
+  if (h_expected != h_actual)
+  {
+    fprintf(stderr, "Expected h at step %i to be %g but is %g\n", step,
+            h_expected, h_actual);
+    return 1;
+  }
+
+  return 0;
+}
+
+int main()
+{
+  SUNContext sunctx;
+  int retval = SUNContext_Create(SUN_COMM_NULL, &sunctx);
+  if (retval != 0)
+  {
+    fprintf(stderr, "SUNContext_Create returned %i\n", retval);
+    return 1;
+  }
+
+  retval = SUNContext_PushErrHandler(sunctx, err_fn, NULL);
+  if (retval != 0)
+  {
+    fprintf(stderr, "SUNContext_PushErrHandler returned %i\n", retval);
+    return 1;
+  }
+
+  const N_Vector y = N_VNew_Serial(1, sunctx);
+  N_VConst(SUN_RCONST(1.0), y);
+
+  void* arkode_mem = ERKStepCreate(f, SUN_RCONST(0.0), y, sunctx);
+
+  const sunrealtype h0           = SUN_RCONST(1.0e-4);
+  const sunrealtype first_growth = SUN_RCONST(1234.0);
+  const sunrealtype growth       = SUN_RCONST(3.0);
+
+  ARKodeSetInitStep(arkode_mem, h0);
+  ARKodeSetMaxFirstGrowth(arkode_mem, first_growth);
+  ARKodeSetMaxGrowth(arkode_mem, growth);
+
+  sunrealtype h_expect = first_growth * h0;
+
+  for (int i = 0; i < 4; i++)
+  {
+    retval = check_step(arkode_mem, y, h_expect);
+    if (retval != 0) { return retval; }
+    h_expect *= growth;
+  }
+
+  ARKodeFree(&arkode_mem);
+  N_VDestroy(y);
+  SUNContext_Free(&sunctx);
+
+  printf("SUCCESS\n");
+
+  return 0;
+}