From 6690077acd1b37b12e1313dddcf17ca739a4b339 Mon Sep 17 00:00:00 2001
From: sjplimp <sjplimp@f3b2605a-c512-4ea7-a41b-209d697bcdaa>
Date: Mon, 3 Dec 2007 15:49:30 +0000
Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@1208
 f3b2605a-c512-4ea7-a41b-209d697bcdaa

---
 src/fix_spring.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/fix_spring.cpp b/src/fix_spring.cpp
index bdefcaa938..a38c64ff86 100644
--- a/src/fix_spring.cpp
+++ b/src/fix_spring.cpp
@@ -63,6 +63,8 @@ FixSpring::FixSpring(LAMMPS *lmp, int narg, char **arg) :
     igroup2 = group->find(arg[4]);
     if (igroup2 == -1) 
       error->all("Could not find fix spring couple group ID"); 
+    if (igroup2 == igroup) 
+      error->all("Two groups cannot be the same in fix spring couple"); 
     group2bit = group->bitmask[igroup2];
     k_spring = atof(arg[5]);
     xflag = yflag = zflag = 1;