Class sym::FixedSizeOptimizer

template<typename ScalarType, typename _NonlinearSolverType = LevenbergMarquardtSolver<ScalarType>>
class FixedSizeOptimizer

Class for optimizing a nonlinear least-squares problem given a linearization function and an optimization state which may be user-defined. This class largely mirrors the Optimizer class, but differs in the following key ways:

  • User-defined state (of type ValuesType) can be used in place of Values objects.

  • A user-defined linearization function can be used in place of the Linearizer class (thus, constructing a list of symforce Factor objects is not required).

Compared to the Optimizer class, these differences allow for more efficient optimization of problems whose structure is know at compile-time by avoiding overhead related to working with dynamically-sized problems. Thus, this class should be preferred over the Optimizer class when the problem structure is known at compile-time.

Example of user-defined types: 

// User-defined values type to store optimized states + constants
struct CustomValuesType {...};

// User defined optimization state
class CustomOptimizationState : public
     sym::internal::LevenbergMarquardtStateBase<CustomOptimizationState, CustomValuesType,
                                                Eigen::SparseMatrix<double>> {
 public:
  // Retracts `Init()` using `update` and stores the result in `New()`
  void UpdateNewFromInitImpl(const sym::VectorX<Scalar>& update, const Scalar epsilon) {...}

  // Optionally returns serialized LCM type to store in iteration states if debugging is
  // enabled
  sym::values_t GetLcmTypeImpl(const ValuesType& values) const {...}
};

// User-defined linearization function
void LinearizeCustomValues(const CustomValuesType& values,
                           sym::SparseLinearizationd& linearization) {...}
Example usage: 
using LinearSolverType = sym::SparseCholeskySolver<Eigen::SparseMatrix<double>>;
using CustomNonlinearSolver =
    sym::LevenbergMarquardtSolver<double, LinearSolverType, CustomOptimizationState>;
using CustomOptimizer = sym::FixedSizeOptimizer<double, CustomNonlinearSolver>;

CustomOptimizer optimizer(DefaultLmParams());
CustomValuesType custom_values{...};
optimizer.Optimize(custom_values, LinearizeCustomValues);
See symforce/test/symforce_fixed_size_optimizer_test.cc for more examples.

Public Types

using Scalar = ScalarType
using NonlinearSolverType = _NonlinearSolverType
using FailureReason = typename NonlinearSolverType::FailureReason
using MatrixType = typename NonlinearSolverType::MatrixType
using Stats = OptimizationStats<MatrixType>
using LinearizeFunc = typename NonlinearSolverType::LinearizeFunc
using ValuesType = typename NonlinearSolverType::ValuesType

Public Functions

FixedSizeOptimizer(const optimizer_params_t &params, const std::string &name = "sym::FixedSizeOptimizer", const Scalar epsilon = sym::kDefaultEpsilon<Scalar>)
template<typename ...NonlinearSolverArgs>
FixedSizeOptimizer(const optimizer_params_t &params, const std::string &name, const Scalar epsilon, NonlinearSolverArgs&&... nonlinear_solver_args)
Stats Optimize(ValuesType &values, const LinearizeFunc &linearize_func, const int num_iterations = -1, const bool populate_best_linearization = false)

Optimize the given values in-place using the given linearization function

Parameters:

  • num_iterations – If < 0 (the default), uses the number of iterations specified by the params at construction

  • populate_best_linearization – If true, the linearization at the best values will be filled out in the stats

Returns:

The optimization stats

void Optimize(ValuesType &values, const LinearizeFunc &linearize_func, int num_iterations, bool populate_best_linearization, Stats &stats)

Optimize the given values in-place using the given linearization function

This overload takes the stats as an argument, and stores into there. This allows users to avoid reallocating memory for any of the entries in the stats, for use cases where that’s important.

Parameters:

  • num_iterations – If < 0 (the default), uses the number of iterations specified by the params at construction

  • populate_best_linearization – If true, the linearization at the best values will be filled out in the stats

  • stats – An OptimizationStats to fill out with the result - if filling out dynamically allocated fields here, will not reallocate if memory is already allocated in the required shape (e.g. for repeated calls to Optimize())

void Optimize(ValuesType &values, const LinearizeFunc &linearize_func, int num_iterations, Stats &stats)

Optimize the given values in-place using the given linearization function

This overload takes the stats as an argument, and stores into there. This allows users to avoid reallocating memory for any of the entries in the stats, for use cases where that’s important.

Parameters:

  • num_iterations – If < 0 (the default), uses the number of iterations specified by the params at construction

  • stats – An OptimizationStats to fill out with the result - if filling out dynamically allocated fields here, will not reallocate if memory is already allocated in the required shape (e.g. for repeated calls to Optimize())

void Optimize(ValuesType &values, const LinearizeFunc &linearize_func, Stats &stats)

Optimize the given values in-place using the given linearization function

This overload takes the stats as an argument, and stores into there. This allows users to avoid reallocating memory for any of the entries in the stats, for use cases where that’s important.

Parameters:

stats – An OptimizationStats to fill out with the result - if filling out dynamically allocated fields here, will not reallocate if memory is already allocated in the required shape (e.g. for repeated calls to Optimize())

void ComputeFullCovariance(const Linearization<MatrixType> &linearization, MatrixX<Scalar> &covariance)

Get the full problem covariance at the given linearization.

The ordering of entries is the same as the order in the hessian computed by the linearization function.

Parameters:

covariance – A matrix that will be filled out with the full problem covariance.

const NonlinearSolverType &NonlinearSolver() const

Get the NonlinearSolver object

NonlinearSolverType &NonlinearSolver()
void UpdateParams(const optimizer_params_t &params)

Update the optimizer params

const optimizer_params_t &Params() const

Get the params used by the nonlinear solver