From 2fc96d0f100b0ba3137263f52f1a9f1ab92a97f6 Mon Sep 17 00:00:00 2001
From: nuclearkevin <66632997+nuclearkevin@users.noreply.github.com>
Date: Mon, 13 Jul 2026 16:06:57 -0500
Subject: [PATCH] Regold MG survival biasing test for the 2-component fix.

---
 src/eigenvalue.cpp                                          | 4 ++--
 tests/regression_tests/mg_survival_biasing/results_true.dat | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/eigenvalue.cpp b/src/eigenvalue.cpp
index f3da02caf1..b2a641f071 100644
--- a/src/eigenvalue.cpp
+++ b/src/eigenvalue.cpp
@@ -585,7 +585,7 @@ int openmc_get_keff(double* k_combined)
     // block matrices of the three estimator equations reduces to scalars here
     // See LA-12658-MS, Eqs. 36 and 40.
 
-    // We can use variance/covariances for the mean as the division by (n - 1)
+    // We can use the \Sigma matrix for the mean as the division by (n - 1)
     // cancels.
     const double f = cov(i, i) + cov(j, j) - 2.0 * cov(i, j);
     const double w_1 = (cov(j, j) - cov(i, j)) / f;
@@ -593,7 +593,7 @@ int openmc_get_keff(double* k_combined)
 
     k_combined[0] = kv[i] * w_1 + kv[j] * w_2;
 
-    // We must use the sums of squares for the variance as the division by
+    // We must use the S matrix for the variance as the division by
     // (n - 1) does not cancel.
     const double s_ii = cov(i, i) * (n - 1);
     const double s_jj = cov(j, j) * (n - 1);
diff --git a/tests/regression_tests/mg_survival_biasing/results_true.dat b/tests/regression_tests/mg_survival_biasing/results_true.dat
index 4b26978ada..4f14ad167a 100644
--- a/tests/regression_tests/mg_survival_biasing/results_true.dat
+++ b/tests/regression_tests/mg_survival_biasing/results_true.dat
@@ -1,2 +1,2 @@
 k-combined:
-9.889968E-01 9.144186E-03
+9.889968E-01 1.823442E-02