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// Ceres Solver - A fast non-linear least squares minimizer
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// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)
//
// CostFunctionToFunctor is an adapter class that allows users to use
// SizedCostFunction objects in templated functors which are to be used for
// automatic differentiation. This allows the user to seamlessly mix
// analytic, numeric and automatic differentiation.
//
// For example, let us assume that
//
// class IntrinsicProjection : public SizedCostFunction<2, 5, 3> {
// public:
// IntrinsicProjection(const double* observation);
// bool Evaluate(double const* const* parameters,
// double* residuals,
// double** jacobians) const override;
// };
//
// is a cost function that implements the projection of a point in its
// local coordinate system onto its image plane and subtracts it from
// the observed point projection. It can compute its residual and
// jacobians either via analytic or numerical differentiation.
//
// Now we would like to compose the action of this CostFunction with
// the action of camera extrinsics, i.e., rotation and
// translation. Say we have a templated function
//
// template<typename T>
// void RotateAndTranslatePoint(const T* rotation,
// const T* translation,
// const T* point,
// T* result);
//
// Then we can now do the following,
//
// struct CameraProjection {
// CameraProjection(const double* observation)
// : intrinsic_projection_(new IntrinsicProjection(observation)) {
// }
// template <typename T>
// bool operator()(const T* rotation,
// const T* translation,
// const T* intrinsics,
// const T* point,
// T* residual) const {
// T transformed_point[3];
// RotateAndTranslatePoint(rotation, translation, point, transformed_point);
//
// // Note that we call intrinsic_projection_, just like it was
// // any other templated functor.
//
// return intrinsic_projection_(intrinsics, transformed_point, residual);
// }
//
// private:
// CostFunctionToFunctor<2,5,3> intrinsic_projection_;
// };
#ifndef CERES_PUBLIC_COST_FUNCTION_TO_FUNCTOR_H_
#define CERES_PUBLIC_COST_FUNCTION_TO_FUNCTOR_H_
#include <cstdint>
#include <numeric>
#include <tuple>
#include <vector>
#include "ceres/cost_function.h"
#include "ceres/dynamic_cost_function_to_functor.h"
#include "ceres/internal/fixed_array.h"
#include "ceres/internal/integer_sequence.h"
#include "ceres/internal/parameter_dims.h"
#include "ceres/internal/port.h"
#include "ceres/types.h"
namespace ceres {
template <int kNumResiduals, int... Ns>
class CostFunctionToFunctor {
public:
// Takes ownership of cost_function.
explicit CostFunctionToFunctor(CostFunction* cost_function)
: cost_functor_(cost_function) {
CHECK(cost_function != nullptr);
CHECK(kNumResiduals > 0 || kNumResiduals == DYNAMIC);
const std::vector<int32_t>& parameter_block_sizes =
cost_function->parameter_block_sizes();
const int num_parameter_blocks = ParameterDims::kNumParameterBlocks;
CHECK_EQ(static_cast<int>(parameter_block_sizes.size()),
num_parameter_blocks);
if (parameter_block_sizes.size() == num_parameter_blocks) {
for (int block = 0; block < num_parameter_blocks; ++block) {
CHECK_EQ(ParameterDims::GetDim(block), parameter_block_sizes[block])
<< "Parameter block size missmatch. The specified static parameter "
"block dimension does not match the one from the cost function.";
}
}
CHECK_EQ(accumulate(
parameter_block_sizes.begin(), parameter_block_sizes.end(), 0),
ParameterDims::kNumParameters);
}
template <typename T, typename... Ts>
bool operator()(const T* p1, Ts*... ps) const {
// Add one because of residual block.
static_assert(sizeof...(Ts) + 1 == ParameterDims::kNumParameterBlocks + 1,
"Invalid number of parameter blocks specified.");
auto params = std::make_tuple(p1, ps...);
// Extract residual pointer from params. The residual pointer is the
// last pointer.
constexpr int kResidualIndex = ParameterDims::kNumParameterBlocks;
T* residuals = std::get<kResidualIndex>(params);
// Extract parameter block pointers from params.
using Indices =
internal::make_integer_sequence<int,
ParameterDims::kNumParameterBlocks>;
std::array<const T*, ParameterDims::kNumParameterBlocks> parameter_blocks =
GetParameterPointers<T>(params, Indices());
return cost_functor_(parameter_blocks.data(), residuals);
}
private:
using ParameterDims = internal::StaticParameterDims<Ns...>;
template <typename T, typename Tuple, int... Indices>
static std::array<const T*, ParameterDims::kNumParameterBlocks>
GetParameterPointers(const Tuple& paramPointers,
internal::integer_sequence<int, Indices...>) {
return std::array<const T*, ParameterDims::kNumParameterBlocks>{
{std::get<Indices>(paramPointers)...}};
}
DynamicCostFunctionToFunctor cost_functor_;
};
} // namespace ceres
#endif // CERES_PUBLIC_COST_FUNCTION_TO_FUNCTOR_H_