From 093f981719a24a25c0aa2a8184c287741b38c615 Mon Sep 17 00:00:00 2001
From: Trung Nguyen <ndactrung@gmail.com>
Date: Sat, 23 May 2020 23:52:00 -0500
Subject: [PATCH] Improved the way body inertia moments are checked if they are
 zero when updating body quaterions in fix rigid/nve

---
 src/math_extra.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/math_extra.cpp b/src/math_extra.cpp
index 797d210d0e..0fe04b6d43 100644
--- a/src/math_extra.cpp
+++ b/src/math_extra.cpp
@@ -258,8 +258,8 @@ void no_squish_rotate(int k, double *p, double *q, double *inertia,
   // obtain phi, cosines and sines
 
   phi = p[0]*kq[0] + p[1]*kq[1] + p[2]*kq[2] + p[3]*kq[3];
-  if (fabs(inertia[k-1]) < 1e-6) phi *= 0.0;
-  else phi /= 4.0 * inertia[k-1];
+  phi /= (4.0 * inertia[k-1]);
+  if (!std::isfinite(phi)) phi = 0.0;
   c_phi = cos(dt * phi);
   s_phi = sin(dt * phi);