From 5991ff6b40b0d1b6cf26db54f549041badb7d3f1 Mon Sep 17 00:00:00 2001
From: Oliver Sander <sander@dune-project.org>
Date: Tue, 9 Oct 2012 16:25:55 +0000
Subject: [PATCH] Add power implementation with run-time mantissa and
compile-time exponent.
Taken from hcube.cc in dune-grid.
We may want to unify the naming eventually.
[[Imported from SVN: r7033]]
---
dune/common/power.hh | 55 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)
diff --git a/dune/common/power.hh b/dune/common/power.hh
index 8ce88b82a..1e2e68fe4 100644
--- a/dune/common/power.hh
+++ b/dune/common/power.hh
@@ -30,6 +30,61 @@ namespace Dune {
enum { power = 1 };
};
+
+ #ifndef DOXYGEN
+ template <int p, bool odd = p%2>
+ struct PowerImp {};
+#endif
+
+ /** \brief Compute power for a run-time mantissa and a compile-time integer exponent
+ *
+ * Does some magic to create efficient code. Not benchmarked AFAIK.
+ *
+ * \tparam p The exponent
+ */
+ template <int p>
+ struct Power
+ {
+ template <typename T>
+ static T eval(const T & a)
+ {
+ return PowerImp<p>::eval(a);
+ }
+ };
+
+#ifndef DOXYGEN
+ template <int p>
+ struct PowerImp<p,false>
+ {
+ template <typename T>
+ static T eval(const T & a)
+ {
+ T t = Power<p/2>::eval(a);
+ return t*t;
+ }
+ };
+
+ template <int p>
+ struct PowerImp<p,true>
+ {
+ template <typename T>
+ static T eval(const T & a)
+ {
+ return a*Power<p-1>::eval(a);;
+ }
+ };
+
+ template <>
+ struct PowerImp<1,true>
+ {
+ template <typename T>
+ static T eval(const T & a)
+ {
+ return a;
+ }
+ };
+#endif
+
}
#endif
--
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