Merge pull request #438 from Smithsonian/feat/ias15-adaptive-mode-2-default

Default the IAS15 integrator to the modern (mode 2) adaptive step controller

Author: matthewholman

src/lib/orbit_fit/orbit_fit.cpp

@@ -63,9 +63,12 @@ namespace orbit_fit
     // the legacy value, apply_ias15_adaptive_mode() must run *after*
     // assist_attach, not before like apply_ias15_min_dt.
     //
-    // Default -1 means "leave ASSIST's choice untouched" (no behavior
-    // change for existing callers).
-    static int g_ias15_adaptive_mode = -1;
+    // Default 2 selects the newer (Pham, Rein & Spiegel 2024) controller on
+    // every freshly-attached sim: it steps through close-Earth encounters
+    // gracefully, whereas the legacy controller (mode 1) drives dt -> 0 and can
+    // hang the fit, at no accuracy cost (correctness is mode-independent).
+    // Set to -1 to leave ASSIST's legacy choice untouched, or 1 to force it.
+    static int g_ias15_adaptive_mode = 2;
 
     inline void set_ias15_adaptive_mode(int m) { g_ias15_adaptive_mode = m; }
     inline int  get_ias15_adaptive_mode(void)  { return g_ias15_adaptive_mode; }

tests/layup/test_ias15_settings.py

@@ -8,21 +8,28 @@
 
 The settings are process-wide (file-scope globals in orbit_fit.cpp), so each
 test saves and restores the prior value to avoid leaking state into other
-tests in the same process.
+tests in the same process. The one fit-based test,
+``test_fit_is_mode_independent``, is guarded by ``requires_ephem``.
 """
 
 from __future__ import annotations
 
 import contextlib
 
+import numpy as np
 import pytest
 
+from _bk_guards import requires_ephem
+from layup.orbitfit import orbitfit
 from layup.routines import (
     get_ias15_adaptive_mode,
     get_ias15_min_dt,
     set_ias15_adaptive_mode,
     set_ias15_min_dt,
 )
+from layup.utilities.data_processing_utilities import parse_fit_result
+from layup.utilities.data_utilities_for_tests import get_test_filepath
+from layup.utilities.file_io.CSVReader import CSVDataReader
 
 
 @contextlib.contextmanager
@@ -65,9 +72,11 @@ def test_min_dt_reset_to_zero():
         assert get_ias15_min_dt() == 0.0
 
 
-def test_adaptive_mode_default_is_unset():
-    """By default adaptive_mode is -1, the sentinel meaning 'do not override'."""
-    assert get_ias15_adaptive_mode() == -1
+def test_adaptive_mode_default_is_two():
+    """The default adaptive_mode is 2, the modern (Pham, Rein & Spiegel 2024)
+    IAS15 step controller, engaged on every freshly-attached sim so close-Earth
+    encounters do not drive the timestep to zero and hang a fit."""
+    assert get_ias15_adaptive_mode() == 2
 
 
 @pytest.mark.parametrize("mode", [0, 1, 2, 3])
@@ -85,3 +94,29 @@ def test_adaptive_mode_reset_to_sentinel():
         assert get_ias15_adaptive_mode() == 2
         set_ias15_adaptive_mode(-1)
         assert get_ias15_adaptive_mode() == -1
+
+
+@requires_ephem
+def test_fit_is_mode_independent():
+    """The IAS15 adaptive controller changes only whether/how fast a fit
+    completes, never the fitted orbit. A well-behaved object fit under the
+    legacy controller (mode 1) and the modern controller (mode 2, the default)
+    returns the same state (bit-for-bit for a well-conditioned arc)."""
+    input_data = CSVDataReader(
+        get_test_filepath("1_random_mpc_ADES_provIDs_no_sats_micro.csv"),
+        "csv",
+        primary_id_column_name="provID",
+    ).read_rows()
+
+    def _fit_state(mode):
+        with _restore_adaptive_mode():
+            set_ias15_adaptive_mode(mode)
+            rows = orbitfit(input_data, cache_dir=None)
+        for row in rows:
+            if row["flag"] == 0:
+                return np.array(parse_fit_result(row).state, dtype=float)
+        raise AssertionError("fit did not converge (flag != 0)")
+
+    legacy = _fit_state(1)
+    modern = _fit_state(2)
+    np.testing.assert_allclose(modern, legacy, rtol=1e-10, atol=1e-12)