Problem When Using DynamicCostFunctionToFunctor

[Adam Hartshorne]

Using the follow simple example, based upon http://ceres-solver.org/nnls_modeling.html?highlight=dynamiccostfunctiontofunctor#dynamiccostfunctiontofunctor , the parameter blocks are correctly passed to the DynCostFunctor, but when the Evaluate method of DynCostFunction is called, the memory supposedly holding the parameters is "unreadable". Perhaps I am missing something?

class DynCostFunction : public ceres::CostFunction {

public:
 DynCostFunction() {}

 virtual bool Evaluate(double const* const* parameters,
 double* residuals,
 double** jacobians) const {

  // NOT POINTING TO ANYWHERE
 const double* sample_params_1 = parameters[0];
 const double* sample_params_2 = parameters[1];

 // FAILS AS CAN'T READ MEMORY STORING PARAMETERS
 std::cout << "(" << sample_params_1[0] << "," << sample_params_1[1] << "," << ")" << "\t (" << sample_params_2[0] << "," << sample_params_2[1] << ")" << std::endl;

 // IN REAL APP, RESIDUAL AND JACOBIAN CALCULATED HERE
 // ...

 return true;
 }

};


class DynCostFunctor {

public:

 std::unique_ptr<ceres::DynamicCostFunctionToFunctor> _compute_via_dyn_cost;

 DynCostFunctor()
 {
 _compute_via_dyn_cost.reset(new ceres::DynamicCostFunctionToFunctor(new DynCostFunction()));
 }


 template<typename T>
 bool operator()(T const* const* parameters, T* residual) const {

 const T* sample_params_1 = parameters[0];
 const T* sample_params_2 = parameters[1];

 // CORRECTLY DISPLAYS THE PARAMETERS STORED IN PARAMETER BLOCKS AS EXPECTED
 std::cout << "(" << sample_params_1[0] << "," << sample_params_1[1] << "," << ")" << "\t (" << sample_params_2[0] << "," << sample_params_2[1] << ")" << std::endl;

 (*_compute_via_dyn_cost)(parameters, residual);

 return true;
 }

};


int main()
{

Problem problem;

const int parameter_1_block_size = 5 ;
const int n_samples = 100 ;
const int n_verts = 8;
const int parameter_2_block_size = n_verts *3 ;

MatrixXd X(parameter_1_block_size, n_samples);
X.setZero();

double lower_bound = 0;
double upper_bound = 1.0;
std::uniform_real_distribution<double> unif(lower_bound, upper_bound);
std::default_random_engine re;

for (auto v : range(0, n_samples)) {
 X(0, v) = v;
 X(1, v) = unif(re);
 X(2, v) = unif(re);
 X(3, v) = unif(re);
 X(4, v) = unif(re);
}


MatrixXd Y(parameter_2_block_size, 1);
Y.setZero();

for (auto v : range(0, parameter_2_block_size)) {
 Y(v) = unif(re);
}

std::vector<double*> parameter_blocks(n_samples+1);

for (auto v : range(0, n_samples)) {
parameter_blocks[v] = X.data() + (parameter_1_block_size * v);
problem.AddParameterBlock(parameter_blocks[v], parameter_1_block_size);
}

parameter_blocks[n_samples] = &Y(0);
problem.AddParameterBlock(parameter_blocks[n_samples], parameter_2_block_size);

ceres::DynamicAutoDiffCostFunction<DynCostFunctor>*
dynamic_sized_cost_function (
new ceres::DynamicAutoDiffCostFunction<DynCostFunctor>(
new DynCostFunctor()));

dynamic_sized_cost_function->AddParameterBlock(parameter_1_block_size);
dynamic_sized_cost_function->AddParameterBlock(parameter_2_block_size);
dynamic_sized_cost_function->SetNumResiduals(3);

for (auto s : range(0, n_samples)) {
problem.AddResidualBlock(
 dynamic_sized_cost_function,
NULL,
parameter_blocks[s],
parameter_blocks[n_samples]);
}

Solver::Options options;
options.max_num_iterations = 50;
options.minimizer_progress_to_stdout = true;
options.function_tolerance = 1e-100;
Solver::Summary summary;

ceres::Solve(options, &problem, &summary);

std::cout << summary.FullReport() << std::endl;

}

[Sameer Agarwal]

Adam,

DynCostFunction does not know its size. You need to call set_num_residuals() and add the size of the parameter blocks to the parameter_block_sizes_ array in its constructor.

Sameer

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[Adam Hartshorne]

Thank you, that did the trick.

FYI anybody finding this thread in the future, see  class CallbackCostFunction : public ceres::CostFunction in /internal/ceres/c_api.cc for an example of how to do it.

Regards,

Adam