From f3caf79806dc7e9fcb4f84b4f5cff1ef70f7605e Mon Sep 17 00:00:00 2001
From: dominiquef <dominiquef@mirageoscience.com>
Date: Fri, 16 May 2025 14:26:20 -0700
Subject: [PATCH 1/3] Prevent lower IRLS start chi than target chi

---
 .../factories/directives_factory.py           | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/simpeg_drivers/components/factories/directives_factory.py b/simpeg_drivers/components/factories/directives_factory.py
index 9cf71b80..bfef3f4e 100644
--- a/simpeg_drivers/components/factories/directives_factory.py
+++ b/simpeg_drivers/components/factories/directives_factory.py
@@ -15,6 +15,7 @@
 from __future__ import annotations
 
 from abc import ABC
+from logging import getLogger
 from typing import TYPE_CHECKING
 
 import numpy as np
@@ -29,6 +30,8 @@
 if TYPE_CHECKING:
     from simpeg_drivers.driver import InversionDriver
 
+logger = getLogger(__name__)
+
 
 class DirectivesFactory:
     def __init__(self, driver: InversionDriver):
@@ -263,7 +266,15 @@ def scale_misfits(self):
     def update_irls_directive(self):
         """Directive to update IRLS."""
         if self._update_irls_directive is None:
-            has_chi_start = self.params.starting_chi_factor is not None
+            start_chi_fact = self.params.starting_chi_factor
+
+            if start_chi_fact is not None and self.params.chi_factor > start_chi_fact:
+                logger.warning(
+                    "Starting chi factor is greater than target chi factor.\n"
+                    "Setting the target chi factor to the starting chi factor."
+                )
+                start_chi_fact = self.params.chi_factor
+
             self._update_irls_directive = directives.UpdateIRLS(
                 f_min_change=self.params.f_min_change,
                 max_irls_iterations=self.params.max_irls_iterations,
@@ -272,11 +283,7 @@ def update_irls_directive(self):
                 cooling_rate=self.params.cooling_rate,
                 cooling_factor=self.params.cooling_factor,
                 irls_cooling_factor=self.params.epsilon_cooling_factor,
-                chifact_start=(
-                    self.params.starting_chi_factor
-                    if has_chi_start
-                    else self.params.chi_factor
-                ),
+                chifact_start=start_chi_fact or self.params.chi_factor,
                 chifact_target=self.params.chi_factor,
             )
         return self._update_irls_directive

From d35d541f2cb3cc80e7798a0c41db46f22a82efd0 Mon Sep 17 00:00:00 2001
From: dominiquef <dominiquef@mirageoscience.com>
Date: Fri, 16 May 2025 14:29:56 -0700
Subject: [PATCH 2/3] Add unitest

---
 tests/driver_test.py | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/tests/driver_test.py b/tests/driver_test.py
index aa99564e..eb2d6ebb 100644
--- a/tests/driver_test.py
+++ b/tests/driver_test.py
@@ -57,3 +57,40 @@ def test_smallness_terms(tmp_path: Path):
         params.alpha_s = None
         driver = GravityInversionDriver(params)
         assert driver.regularization.objfcts[0].alpha_s == 0.0
+
+
+def test_target_chi(tmp_path: Path, caplog):
+    n_grid_points = 2
+    refinement = (2,)
+
+    geoh5, _, model, survey, topography = setup_inversion_workspace(
+        tmp_path,
+        background=0.0,
+        anomaly=0.75,
+        n_electrodes=n_grid_points,
+        n_lines=n_grid_points,
+        refinement=refinement,
+        flatten=False,
+    )
+
+    with geoh5.open():
+        gz = survey.add_data({"gz": {"values": np.ones(survey.n_vertices)}})
+        mesh = model.parent
+        active_cells = ActiveCellsOptions(topography_object=topography)
+        params = GravityInversionOptions(
+            geoh5=geoh5,
+            mesh=mesh,
+            active_cells=active_cells,
+            data_object=gz.parent,
+            gz_channel=gz,
+            gz_uncertainty=2e-3,
+            starting_model=1e-4,
+            starting_chi_factor=1.0,
+            chi_factor=2.0,
+        )
+        driver = GravityInversionDriver(params)
+
+        with caplog.at_level("WARNING"):
+            assert driver.directives.update_irls_directive.chifact_start == 2.0
+
+        assert "Starting chi factor is greater" in caplog.text

From dff5b3fc68164de645ea05652aa19ad36ea0f137 Mon Sep 17 00:00:00 2001
From: dominiquef <dominiquef@mirageoscience.com>
Date: Fri, 16 May 2025 14:38:24 -0700
Subject: [PATCH 3/3] Change cooling rate type

---
 simpeg_drivers/joint/options.py | 2 +-
 simpeg_drivers/options.py       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/simpeg_drivers/joint/options.py b/simpeg_drivers/joint/options.py
index abf871c3..7e033bae 100644
--- a/simpeg_drivers/joint/options.py
+++ b/simpeg_drivers/joint/options.py
@@ -84,7 +84,7 @@ class BaseJointOptions(BaseData):
     initial_beta: float | None = None
     cooling_factor: float = 2.0
 
-    cooling_rate: float = 1.0
+    cooling_rate: int = 1
     max_global_iterations: int = 50
     max_line_search_iterations: int = 20
     max_cg_iterations: int = 30
diff --git a/simpeg_drivers/options.py b/simpeg_drivers/options.py
index 403ffaeb..5b8f0c53 100644
--- a/simpeg_drivers/options.py
+++ b/simpeg_drivers/options.py
@@ -362,7 +362,7 @@ class BaseInversionOptions(CoreOptions):
     initial_beta: float | None = None
     cooling_factor: float = 2.0
 
-    cooling_rate: float = 1.0
+    cooling_rate: int = 1
     max_global_iterations: int = 50
     max_line_search_iterations: int = 20
     max_cg_iterations: int = 30