smash::Integrator Class Reference

#include <integrate.h>

A C++ interface for numerical integration in one dimension with the GSL CQUAD integration functions.

Example:

Integrator integrate;
const auto result = integrate(0.1, 0.9, [](double x) { return x * x; });

Definition at line 106 of file integrate.h.

Public Member Functions
	Integrator (size_t workspace_size=1000)
	Construct an integration functor with the given workspace_size. More...
template<typename F >
Result	operator() (double a, double b, F &&fun)
	The function call operator implements the integration functionality. More...
void	set_precision (double absolute, double relative)
	Set precision for the absolute and relative error of the integration. More...

Private Attributes
std::unique_ptr< gsl_integration_cquad_workspace, GslWorkspaceDeleter >	workspace_
	Holds the workspace pointer. More...
double	accuracy_absolute_ = 1.0e-9
	Parameter to the GSL integration function: desired absolute error limit. More...
double	accuracy_relative_ = 5.0e-4
	Parameter to the GSL integration function: desired relative error limit. More...

Constructor & Destructor Documentation

Integrator()

smash::Integrator::Integrator ( size_t  workspace_size = 1000 )

inlineexplicit

Construct an integration functor with the given workspace_size.

Note

Since the workspace is allocated in the constructor and deallocated on destruction, you should not recreate Integrator objects unless required. Thus, if you want to calculate multiple integrals with the same workspace_size, keep the Integrator object around.

Parameters

workspace_size

The internal workspace is allocated such that it can hold the given number of double precision intervals, their integration results, and error estimates. It also determines the maximum number of subintervals the integration algorithm will use.

Definition at line 122 of file integrate.h.

      : workspace_(gsl_integration_cquad_workspace_alloc(workspace_size)) {}

Member Function Documentation

operator()()

template<typename F >

Result smash::Integrator::operator() ( double  a, double  b, F &&  fun  )

inline

The function call operator implements the integration functionality.

Parameters

[in]	a	The lower limit of the integral.
[in]	b	The upper limit of the integral.

Template Parameters

F	Type of the integrand function.

Parameters

[in]

fun

The callable to integrate over. This callable may be a function pointer, lambda, or a functor object. In any case, the callable must return a double and take a single double argument. If you want to pass additional data to the callable you can e.g. use lambda captures.

Returns

Pair of integral value and absolute error estimate.

Definition at line 139 of file integrate.h.

                                                 {
    Result result;
    const gsl_function gslfun{
        /* important! The lambda cannot use captures, otherwise the
         * conversion to a function pointer type is impossible. */
        [](double x, void *type_erased) -> double {
          auto &&f = *static_cast<F *>(type_erased);
          return f(x);
        },
        &fun};
    // We disable float traps when calling GSL code we cannot control.
    DisableFloatTraps guard;
    const int error_code = gsl_integration_cquad(
        &gslfun, a, b, accuracy_absolute_, accuracy_relative_, workspace_.get(),
        &result.first, &result.second,
        nullptr /* Don't store the number of evaluations */);
    if (error_code) {
      std::stringstream err;
      err << "GSL 1D deterministic integration: " << gsl_strerror(error_code);
      throw std::runtime_error(err.str());
    }
    result.check_error("GSL 1D deterministic integration", accuracy_relative_,
                       accuracy_absolute_);
    return result;
  }

set_precision()

void smash::Integrator::set_precision ( double  absolute, double  relative  )

inline

Set precision for the absolute and relative error of the integration.

Definition at line 168 of file integrate.h.

                                                       {
    accuracy_absolute_ = absolute;
    accuracy_relative_ = relative;
  }

Member Data Documentation

workspace_

std::unique_ptr<gsl_integration_cquad_workspace, GslWorkspaceDeleter> smash::Integrator::workspace_

private

Holds the workspace pointer.

Definition at line 176 of file integrate.h.

accuracy_absolute_

double smash::Integrator::accuracy_absolute_ = 1.0e-9

private

Parameter to the GSL integration function: desired absolute error limit.

Definition at line 179 of file integrate.h.

accuracy_relative_

double smash::Integrator::accuracy_relative_ = 5.0e-4

private

Parameter to the GSL integration function: desired relative error limit.

Definition at line 182 of file integrate.h.

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The documentation for this class was generated from the following file:

• src/include/smash/integrate.h