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release/4.3a0
dellaert 2014-10-08 17:28:33 +02:00
parent 4ac065fab4
commit 6a1bc6e242
1 changed files with 19 additions and 9 deletions
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28
gtsam_unstable/nonlinear/Expression-inl.h
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@ -32,7 +32,15 @@ class Expression;
typedef std::map<Key, Matrix> JacobianMap;
//-----------------------------------------------------------------------------
/// The JacobinaTrace class records a tree-structured expression's execution
struct JacobianTrace {
/**
* The Pointer class is a tagged union that obviates the need to create
* a JacobianTrace subclass for Constants and Leaf Expressions. Instead
* the key for the leaf is stored in the space normally used to store a
* JacobianTrace*. Nothing is stored for a Constant.
*/
///
class Pointer {
enum {
Constant, Leaf, Function
@ -46,41 +54,43 @@ struct JacobianTrace {
Pointer() :
type(Constant) {
}
/// Destructor cleans up pointer if Function
~Pointer() {
if (type == Function)
delete content.ptr;
}
/// Change pointer to a Leaf Trace
void setLeaf(Key key) {
type = Leaf;
content.key = key;
}
/// Take ownership of pointer to a Function Trace
void setFunction(JacobianTrace* trace) {
type = Function;
content.ptr = trace;
}
// Either add to Jacobians (Leaf) or propagate (Function)
// Either insert identity into Jacobians (Leaf) or propagate (Function)
template<class T>
void reverseAD(JacobianMap& jacobians) const {
if (type == Function)
content.ptr->reverseAD(jacobians);
else if (type == Leaf) {
if (type == Leaf) {
size_t n = T::Dim();
jacobians[content.key] = Eigen::MatrixXd::Identity(n, n);
}
} else if (type == Function)
content.ptr->reverseAD(jacobians);
}
// Either add to Jacobians (Leaf) or propagate (Function)
void reverseAD(const Matrix& dTdA, JacobianMap& jacobians) const {
if (type == Function)
content.ptr->reverseAD(dTdA, jacobians);
else if (type == Leaf) {
if (type == Leaf) {
JacobianMap::iterator it = jacobians.find(content.key);
if (it != jacobians.end())
it->second += dTdA;
else
jacobians[content.key] = dTdA;
}
} else if (type == Function)
content.ptr->reverseAD(dTdA, jacobians);
}
};
/// Make sure destructor is virtual
virtual ~JacobianTrace() {
}
virtual void reverseAD(JacobianMap& jacobians) const = 0;