From 93f40364826ff36218cc3e681599282f718828ee Mon Sep 17 00:00:00 2001
From: Oliver Sander <sander@igpm.rwth-aachen.de>
Date: Thu, 21 Apr 2011 10:35:22 +0000
Subject: [PATCH] adjust the bounds for when to use the series expansions for
the derivatives of arccos squared
[[Imported from SVN: r7196]]
---
dune/gfe/unitvector.hh | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/dune/gfe/unitvector.hh b/dune/gfe/unitvector.hh
index de6df3f9..17116adc 100644
--- a/dune/gfe/unitvector.hh
+++ b/dune/gfe/unitvector.hh
@@ -20,9 +20,9 @@ class UnitVector
/** \brief Compute the derivative of arccos^2 without getting unstable for x close to 1 */
static double derivativeOfArcCosSquared(const double& x) {
- const double eps = 1e-12;
+ const double eps = 1e-4;
if (x > 1-eps) { // regular expression is unstable, use the series expansion instead
- return -2 + 2*(x-1)/3 - 4/15*(x-1)*(x-1) + 4/35*(x-1)*(x-1)*(x-1);
+ return -2 + 2*(x-1)/3 - 4/15*(x-1)*(x-1);
} else if (x < -1+eps) { // The function is not differentiable
DUNE_THROW(Dune::Exception, "arccos^2 is not differentiable at x==-1!");
} else
@@ -31,7 +31,7 @@ class UnitVector
/** \brief Compute the second derivative of arccos^2 without getting unstable for x close to 1 */
static double secondDerivativeOfArcCosSquared(const double& x) {
- const double eps = 1e-12;
+ const double eps = 1e-4;
if (x > 1-eps) { // regular expression is unstable, use the series expansion instead
return 2.0/3 - 8*(x-1)/15;
} else if (x < -1+eps) { // The function is not differentiable
@@ -42,7 +42,7 @@ class UnitVector
/** \brief Compute the third derivative of arccos^2 without getting unstable for x close to 1 */
static double thirdDerivativeOfArcCosSquared(const double& x) {
- const double eps = 1e-12;
+ const double eps = 1e-4;
if (x > 1-eps) { // regular expression is unstable, use the series expansion instead
return -8.0/15 + 24*(x-1)/35;
} else if (x < -1+eps) { // The function is not differentiable
--
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