From 0538b96f9ee14e08ed22cb1a9be013be509e30cc Mon Sep 17 00:00:00 2001
From: Filip Leonarski <filip.leonarski@psi.ch>
Date: Thu, 22 Jan 2026 16:33:29 +0100
Subject: [PATCH] XtalOptimizer: Bring back standard loss function for least
 squares

---
 image_analysis/geom_refinement/XtalOptimizer.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/image_analysis/geom_refinement/XtalOptimizer.cpp b/image_analysis/geom_refinement/XtalOptimizer.cpp
index 54fe8d3a..a3e6ac39 100644
--- a/image_analysis/geom_refinement/XtalOptimizer.cpp
+++ b/image_analysis/geom_refinement/XtalOptimizer.cpp
@@ -126,10 +126,9 @@ struct XtalResidual {
 
         auto e_pred_hkl = e_latt.transpose() * e_obs_recip;
 
-        T dh = exp_h - e_pred_hkl[0];
-        T dk = exp_k - e_pred_hkl[1];
-        T dl = exp_l - e_pred_hkl[2];
-        residual[0] = ceres::sqrt(dh * dh + dk * dk + dl * dl);
+        residual[0] = exp_h - e_pred_hkl[0];
+        residual[1] = exp_k - e_pred_hkl[1];
+        residual[2] = exp_l - e_pred_hkl[2];
 
         return true;
     }
@@ -456,14 +455,14 @@ bool XtalOptimizerInternal(XtalOptimizerData &data,
                 continue;
 
             problem.AddResidualBlock(
-                new ceres::AutoDiffCostFunction<XtalResidual, 1, 1, 1, 1, 2, 3, 3, 3>(
+                new ceres::AutoDiffCostFunction<XtalResidual, 3, 1, 1, 1, 2, 3, 3, 3>(
                     new XtalResidual(pt.x, pt.y,
                                      data.geom.GetWavelength_A(),
                                      data.geom.GetPixelSize_mm(),
                                      gonio_back_rot,
                                      h, k, l,
                                      data.crystal_system)),
-                new ceres::CauchyLoss(loss_scale),
+                nullptr,
                 &beam_x,
                 &beam_y,
                 &distance_mm,
@@ -608,5 +607,6 @@ bool XtalOptimizerInternal(XtalOptimizerData &data,
 bool XtalOptimizer(XtalOptimizerData &data, const std::vector<SpotToSave> &spots) {
     if (!XtalOptimizerInternal(data, spots, 0.3))
         return false;
+    XtalOptimizerInternal(data, spots, 0.2);
     return XtalOptimizerInternal(data, spots, 0.1);
 }