From 70181745c9eeb85267ee52ae1a5fa3c261d86c38 Mon Sep 17 00:00:00 2001
From: Henry Weller <http://openfoam.org>
Date: Fri, 22 Jun 2018 12:05:36 +0100
Subject: [PATCH] ODESolvers/seulex: Documented the current
 stability/monotonicity check

---
 src/ODE/ODESolvers/seulex/seulex.C | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/ODE/ODESolvers/seulex/seulex.C b/src/ODE/ODESolvers/seulex/seulex.C
index 643c1c8fc2..1dbb6ee02a 100644
--- a/src/ODE/ODESolvers/seulex/seulex.C
+++ b/src/ODE/ODESolvers/seulex/seulex.C
@@ -153,8 +153,13 @@ bool Foam::seulex::seul
 
             LUBacksubstitute(a_, pivotIndices_, dy_);
 
+            // This form from the original paper is unreliable
+            // step size underflow for some cases
             // const scalar denom = max(1, dy1);
+
+            // This form is reliable but limits how large the step size can be
             const scalar denom = min(1, dy1 + small);
+
             scalar dy2 = 0;
             for (label i=0; i<n_; i++)
             {