From 9dafdb468e8e157469a51470e172c19ea254dce5 Mon Sep 17 00:00:00 2001
From: Oliver Sander <sander@igpm.rwth-aachen.de>
Date: Thu, 11 Feb 2010 21:39:58 +0000
Subject: [PATCH] implement derivativeOfDistanceSquaredWRTSecondArgument()
[[Imported from SVN: r5547]]
---
src/realtuple.hh | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/src/realtuple.hh b/src/realtuple.hh
index c16fe23a..d0a3b34e 100644
--- a/src/realtuple.hh
+++ b/src/realtuple.hh
@@ -48,6 +48,14 @@ public:
return -gradient/distance(a,b);
}
+ /** \brief Compute the gradient of the squared distance function keeping the first argument fixed
+
+ Unlike the distance itself the squared distance is differentiable at zero
+ */
+ static EmbeddedTangentVector derivativeOfDistanceSquaredWRTSecondArgument(const RealTuple& a, const RealTuple& b) {
+ return -2*(a.data_ - b.data_);
+ }
+
/** \brief Write LocalKey object to output stream */
friend std::ostream& operator<< (std::ostream& s, const RealTuple& realTuple)
{
--
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