From 5310d81cacf948290d2e2507a7a140c2d9f21a37 Mon Sep 17 00:00:00 2001
From: Francois Gygi <fgygi@ucdavis.edu>
Date: Thu, 27 Jul 2017 10:31:26 -0700
Subject: [PATCH] Fix discontinuity in torsion constraint function

---
 src/TorsionConstraint.C | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/TorsionConstraint.C b/src/TorsionConstraint.C
index db192d2..56d5168 100644
--- a/src/TorsionConstraint.C
+++ b/src/TorsionConstraint.C
@@ -348,7 +348,11 @@ double TorsionConstraint::sigma(D3vector a, D3vector b,
  D3vector c, D3vector d) const
 {
   // compute the constraint function
-  return torsion_angle(a,b,c,d) - angle_;
+  double delta = torsion_angle(a,b,c,d) - angle_;
+  // account for discontinuity at +/- 180 deg
+  if ( delta >  180.0 ) delta -= 360.0;
+  if ( delta < -180.0 ) delta += 360.0;
+  return delta;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
--
libgit2 0.26.0