From 80f3c9d24dd61204a66a9d099c4b74fb818d6daf Mon Sep 17 00:00:00 2001
From: Ray Speth <speth@mit.edu>
Date: Tue, 22 Jan 2013 20:28:34 +0000
Subject: [PATCH] [1D] Fixed a case where the Newton solver could get stuck

Sometimes, while trying to solve the steady-state problem, the Newton solver
would get stuck in a loop where it couldn't find a suitable damping ratio even
after re-revaluating the Jacobian, causing it to get stuck in an loop where it
would keep re-evaluating the Jacobian at the same point (i.e. without having
made a successful damped step).

This change detects this condition and stops the Newton solver so that the 1D
solver can advance the solution by timestepping before trying to solve the
steady-state problem again.
---
 src/oneD/MultiNewton.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/oneD/MultiNewton.cpp b/src/oneD/MultiNewton.cpp
index b40ce8185..83fec909c 100644
--- a/src/oneD/MultiNewton.cpp
+++ b/src/oneD/MultiNewton.cpp
@@ -312,6 +312,7 @@ int MultiNewton::solve(doublereal* x0, doublereal* x1,
     bool frst = true;
     doublereal rdt = r.rdt();
     int j0 = jac.nEvals();
+    int nJacReeval = 0;
 
     while (1 > 0) {
 
@@ -370,6 +371,10 @@ int MultiNewton::solve(doublereal* x0, doublereal* x1,
         else if (m < 0) {
             if (jac.age() > 1) {
                 forceNewJac = true;
+                if (nJacReeval > 3) {
+                    goto done;
+                }
+                nJacReeval++;
                 if (loglevel > 0)
                     writelog("\nRe-evaluating Jacobian, since no damping "
                              "coefficient\ncould be found with this Jacobian.\n");