Inline Jet initialization in Autodiff
Inlining the Jet initialzation is mandatory for good performance
in autodiff, because all the constants in the dual part can be
propagated into the cost functor.
This patch unrolls the initialization loop with templates and adds
EIGEN_ALWAYS_INLINE to the constructors.
Change-Id: Ic89d645984f3e1df6c63948236da823ba60d9620
diff --git a/include/ceres/internal/autodiff.h b/include/ceres/internal/autodiff.h
index 0bc41f2..cefcfb4 100644
--- a/include/ceres/internal/autodiff.h
+++ b/include/ceres/internal/autodiff.h
@@ -181,14 +181,24 @@
//
// is what would get put in dst if N was 3, offset was 3, and the jet type JetT
// was 8-dimensional.
-template <int Offset, int N, typename T, typename JetT>
-inline void Make1stOrderPerturbation(const T* src, JetT* dst) {
- DCHECK(src);
- DCHECK(dst);
- for (int j = 0; j < N; ++j) {
- dst[j] = JetT(src[j], Offset + j);
+template <int j, int N, int Offset, typename T, typename JetT>
+struct Make1stOrderPerturbation {
+ public:
+ static void Apply(const T* src, JetT* dst) {
+ if (j == 0) {
+ DCHECK(src);
+ DCHECK(dst);
+ }
+ dst[j] = JetT(src[j], j + Offset);
+ Make1stOrderPerturbation<j + 1, N, Offset, T, JetT>::Apply(src, dst);
}
-}
+};
+
+template <int N, int Offset, typename T, typename JetT>
+struct Make1stOrderPerturbation<N, N, Offset, T, JetT> {
+ public:
+ static void Apply(const T* src, JetT* dst) {}
+};
// Calls Make1stOrderPerturbation for every parameter block.
//
@@ -208,7 +218,8 @@
Offset> {
template <typename T, typename JetT>
static void Apply(T const* const* parameters, JetT* x) {
- Make1stOrderPerturbation<Offset, N>(parameters[ParameterIdx], x + Offset);
+ Make1stOrderPerturbation<0, N, Offset, T, JetT>::Apply(
+ parameters[ParameterIdx], x + Offset);
Make1stOrderPerturbations<integer_sequence<int, Ns...>,
ParameterIdx + 1,
Offset + N>::Apply(parameters, x);
