codi::GradientAccessTapeInterface< T_Gradient, T_Identifier > Struct Template Reference

Allow for a direct access to the gradient information computed by the tape. More...

#include <gradientAccessTapeInterface.hpp>

Inheritance diagram for codi::GradientAccessTapeInterface< T_Gradient, T_Identifier >:

Public Types
using	Gradient = T_Gradient
	See GradientAccessTapeInterface.
using	Identifier = T_Identifier
	See GradientAccessTapeInterface.

Public Member Functions
Interface definition
void	setGradient (Identifier const &identifier, Gradient const &gradient, AdjointsManagement adjointsManagement=AdjointsManagement::Automatic)
	Set the gradient.
Gradient const &	getGradient (Identifier const &identifier, AdjointsManagement adjointsManagement=AdjointsManagement::Automatic) const
	Set the gradient.
Gradient &	gradient (Identifier const &identifier, AdjointsManagement adjointsManagement=AdjointsManagement::Automatic)
	Reference access to gradient.
Gradient const &	gradient (Identifier const &identifier, AdjointsManagement adjointsManagement=AdjointsManagement::Automatic) const
	Constant reference access to gradient.

Detailed Description

template<typename T_Gradient, typename T_Identifier>
struct codi::GradientAccessTapeInterface< T_Gradient, T_Identifier >

Allow for a direct access to the gradient information computed by the tape.

See Tape Interface Design for a general overview of the tape interface design in CoDiPack.

The gradient information is usually accessed via the helper functions of the ActiveType, for example

ActiveType<Tape> w = 1.0;
 
w.gradient() = 100.0;
 
std::cout << "Gradient of w: " << w.getGradient() << std::endl;

These helper function are shortcuts to the functions provided in this interface, but the functions here can also be used to obtain the sensitivity information of a variable that is no longer present, for example (documentation/examples/gradientAccessTapeInterface.cpp):

  using Real = codi::RealReverse;
  using Tape = typename Real::Tape;
  using Identifier = typename Tape::Identifier;
 
  Tape& tape = Real::getTape();
 
  Identifier x_in;
  Identifier x_out;
  {
    Real x = 10.0;
 
    tape.setActive();
    tape.registerInput(x);
    x_in = x.getIdentifier(); // Identifier of x when it is defined as an input
 
    // Do some heavy computation
    x = 42.0 * x * x;
 
    tape.registerOutput(x);
    x_out = x.getIdentifier(); // Identifier of x when it is defined as an output
 
    tape.setPassive();
  }
 
  tape.setGradient(x_out, 1.0); // Use this interface to set the gradient of x when it was defined as an output
  tape.evaluate();
 
  std::cout << "Gradient of df/dx: " << tape.getGradient(x_in) << std::endl;

Template Parameters

T_Gradient	The gradient type of a tape, usually chosen as ActiveType::Gradient.
T_Identifier	The adjoint/tangent identification of a tape, usually chosen as ActiveType::Identifier.

Member Function Documentation

getGradient()

template<typename T_Gradient , typename T_Identifier >

Gradient const & codi::GradientAccessTapeInterface< T_Gradient, T_Identifier >::getGradient	(	Identifier const &	identifier,
		AdjointsManagement	adjointsManagement = AdjointsManagement::Automatic
	)		const

Set the gradient.

Automatic adjoints management involves bounds checking and locking. If no adjoint variable with the given identifier exists, a reference to adjoints[0] is returned. See AdjointsManagement for details.

gradient() [1/2]

template<typename T_Gradient , typename T_Identifier >

Gradient & codi::GradientAccessTapeInterface< T_Gradient, T_Identifier >::gradient	(	Identifier const &	identifier,
		AdjointsManagement	adjointsManagement = AdjointsManagement::Automatic
	)

Reference access to gradient.

Automatic adjoints management involves bounds checking, resizing, and locking, see AdjointsManagement for details.

gradient() [2/2]

template<typename T_Gradient , typename T_Identifier >

Gradient const & codi::GradientAccessTapeInterface< T_Gradient, T_Identifier >::gradient	(	Identifier const &	identifier,
		AdjointsManagement	adjointsManagement = AdjointsManagement::Automatic
	)		const

Constant reference access to gradient.

Automatic adjoints management involves bounds checking and locking. If no adjoint variable with the given identifier exists, a reference to adjoints[0] is returned. See AdjointsManagement for details.

setGradient()

template<typename T_Gradient , typename T_Identifier >

void codi::GradientAccessTapeInterface< T_Gradient, T_Identifier >::setGradient	(	Identifier const &	identifier,
		Gradient const &	gradient,
		AdjointsManagement	adjointsManagement = AdjointsManagement::Automatic
	)

Set the gradient.

Automatic adjoints management involves bounds checking, resizing, and locking, see AdjointsManagement for details.

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

• include/codi/tapes/interfaces/gradientAccessTapeInterface.hpp