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authorTavian Barnes <tavianator@gmail.com>2010-10-13 15:45:40 -0400
committerTavian Barnes <tavianator@gmail.com>2010-10-13 17:51:10 -0400
commit2829763fc5f9d222a966402bf073083dbc1da51c (patch)
treeffd1a0df6f6db26aa98c273faf4fef509d3e024a /src/vZ/Adaptive.hpp
parentdbd081ad1808d4e8550dd23971b60b862c7904e0 (diff)
downloadvz-2829763fc5f9d222a966402bf073083dbc1da51c.tar.xz
Implement FSAL.
Diffstat (limited to 'src/vZ/Adaptive.hpp')
-rw-r--r--src/vZ/Adaptive.hpp47
1 files changed, 40 insertions, 7 deletions
diff --git a/src/vZ/Adaptive.hpp b/src/vZ/Adaptive.hpp
index f0cfed1..a422bb4 100644
--- a/src/vZ/Adaptive.hpp
+++ b/src/vZ/Adaptive.hpp
@@ -50,10 +50,7 @@ namespace vZ
GenericAdaptiveIntegrator(Function f, unsigned int order,
ACoefficients a, BCoefficients b,
- BCoefficients bStar)
- : GenericRKIntegrator<Y>(f), m_order(order), m_rejections(0),
- m_a(a), m_b(b), m_bStar(bStar)
- { }
+ BCoefficients bStar);
virtual ~GenericAdaptiveIntegrator() { }
void step();
@@ -64,6 +61,9 @@ namespace vZ
unsigned int m_rejections;
ACoefficients m_a;
BCoefficients m_b, m_bStar;
+
+ bool m_fsal, m_k1Set;
+ Y m_k1;
};
// Type alias
@@ -72,18 +72,45 @@ namespace vZ
// Implementations
template <typename Y>
+ GenericAdaptiveIntegrator<Y>::GenericAdaptiveIntegrator(
+ Function f, unsigned int order,
+ ACoefficients a, BCoefficients b, BCoefficients bStar
+ )
+ : GenericRKIntegrator<Y>(f), m_order(order), m_rejections(0),
+ m_a(a), m_b(b), m_bStar(bStar), m_fsal(true), m_k1Set(false)
+ {
+ std::size_t i;
+ for (i = 0; i < m_a.back().size(); ++i) {
+ if (m_a.back()[i] != m_b.at(i)) {
+ m_fsal = false;
+ return;
+ }
+ }
+
+ if (m_b.at(i) != Scalar(0))
+ m_fsal = false;
+ }
+
+ template <typename Y>
void
GenericAdaptiveIntegrator<Y>::step()
{
static const Scalar S = Scalar(19)/Scalar(20); // Arbitrary saftey factor
Scalar newH = this->h();
Y y;
+ KVector k;
// Attempt the integration step in a loop
while (true) {
- KVector k = calculateK(m_a);
- y = calculateY(k, m_b);
- Y yStar = calculateY(k, m_bStar);
+ if (m_k1Set) {
+ k = calculateK(m_k1, y, m_a);
+ } else if (m_fsal) {
+ k = calculateK(y, m_a);
+ } else {
+ k = calculateK(m_a);
+ y = calculateY(k, m_b);
+ }
+ Y yStar = calculateY(k, m_bStar);
// Get an error estimate
@@ -111,6 +138,12 @@ namespace vZ
this->y(y);
this->x(this->x() + this->h());
+ // Handle FSAL optimization
+ if (m_fsal) {
+ m_k1Set = true;
+ m_k1 = k.back();
+ }
+
// Adjust the stepsize for the next iteration
this->h(newH);
}