From c04dd4f6d60af7f389b28bec864d5bfdd99338e1 Mon Sep 17 00:00:00 2001
From: Massimiliano Bonomi <massimiliano.bonomi@gmail.com>
Date: Sun, 18 Mar 2018 14:17:25 +0100
Subject: [PATCH] fix Q switch function derivatives for large distances
(cherry picked from commit ae6c8ee498c081aa7372c2f6ec77a770ed5cf08a)
---
src/tools/SwitchingFunction.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/tools/SwitchingFunction.cpp b/src/tools/SwitchingFunction.cpp
index dd64f0ffc..de3662fe6 100644
--- a/src/tools/SwitchingFunction.cpp
+++ b/src/tools/SwitchingFunction.cpp
@@ -392,8 +392,9 @@ double SwitchingFunction::calculate(double distance,double&dfunc)const {
} else if(type==nativeq) {
double rdist2 = beta*(distance - lambda * ref);
double exprdist=exp(rdist2);
+ double exprmdist=1.0/exprdist;
result=1./(1.+exprdist);
- dfunc=-exprdist/(1.+exprdist)/(1.+exprdist);
+ dfunc=-1.0/(exprmdist+1.0)/(1.+exprdist);
} else if(type==gaussian) {
result=exp(-0.5*rdist*rdist);
dfunc=-rdist*result;
--
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