codi::ManualStatementPushTapeInterface< T_Real, T_Gradient, T_Identifier > Struct Template Reference

Add derivative information for custom operations to the tape. More...

#include <manualStatementPushTapeInterface.hpp>

Inheritance diagram for codi::ManualStatementPushTapeInterface< T_Real, T_Gradient, T_Identifier >:

Public Types
using	Gradient = T_Gradient
	See ManualStatementPushTapeInterface.
using	Identifier = T_Identifier
	See ManualStatementPushTapeInterface.
using	Real = T_Real
	See ManualStatementPushTapeInterface.

Public Member Functions
Interface definition
void	pushJacobianManual (Real const &jacobian, Real const &value, Identifier const &index)
void	storeManual (Real const &lhsValue, Identifier &lhsIndex, Config::ArgumentSize const &size)

Detailed Description

template<typename T_Real, typename T_Gradient, typename T_Identifier>
struct codi::ManualStatementPushTapeInterface< T_Real, T_Gradient, T_Identifier >

Add derivative information for custom operations to the tape.

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

The functions in this interface can be used to provide derivative information to CoDiPack for functions that are not known to CoDiPack but so small that an external function implementation is an overkill.

The forward and reverse AD equations are the base for this interface. The user has to provide the Jacobian for all arguments and compute the value for .

Before the call to storeManual the user has to update the value of the output, that is, in the above equations. This is usually done with output.value() = w. Afterwards, storeManual() has to be called. The size argument is the number of arguments from the equations above. This call ensures that output gets a proper identifier and the dependency chain is not broken or wrong for this variable.

Afterwards the user has to call pushJacobianManual() for each argument .

The user has to ensure that the computations of the Jacobians are evaluated such that the CoDiPack tape does not accidentally record them.

Here is an example for manual statement push (documentation/examples/manualStatementPushTapeInterface.cpp):

using Real = codi::RealReverse;
using Tape = typename Real::Tape;
 
using Primal = typename Real::Real;
 
Primal func(Primal x, Primal y) {
  return sqrt(x * x + y * y);
}
 
Primal func_dx(Primal x, Primal y) {
  return x / func(x, y);
}
 
Primal func_dy(Primal x, Primal y) {
  return y / func(x, y);
}
 
int main(int nargs, char** args) {
 
  Tape& tape = Real::getTape();
 
  // Recording
  Real u1 = 10.0;
  Real u2 = 4.0;
 
  tape.setActive();
  tape.registerInput(u1);
  tape.registerInput(u2);
 
  Real w = func(u1.value(), u2.value());
  tape.storeManual(w.value(), w.getIdentifier(), 2);
  tape.pushJacobianManual(func_dx(u1.value(), u2.value()), u1.value(), u1.getIdentifier());
  tape.pushJacobianManual(func_dy(u1.value(), u2.value()), u2.value(), u2.getIdentifier());
 
  tape.registerOutput(w);
  tape.setPassive();
 
  // Reverse evaluation
  w.setGradient(1.0);
  tape.evaluate();
 
  std::cout << "Gradient of dy/du1: " << u1.getGradient() << std::endl;
  std::cout << "Gradient of dy/du2: " << u2.getGradient() << std::endl;
}

Template Parameters

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

Member Function Documentation

pushJacobianManual()

template<typename T_Real , typename T_Gradient , typename T_Identifier >

void codi::ManualStatementPushTapeInterface< T_Real, T_Gradient, T_Identifier >::pushJacobianManual	(	Real const &	jacobian,
		Real const &	value,
		Identifier const &	index
	)

Push a Jacobian entry to the tape. storeManual() has to be called first and is passed the number of arguments. Afterwards, this method has to be called once for each argument.

Parameters

jacobian	Jacobian of the argument .
value	Value of the argument . Usually u_i.value().
index	Identifier of the argument . Usually u_i.identifier().

storeManual()

template<typename T_Real , typename T_Gradient , typename T_Identifier >

void codi::ManualStatementPushTapeInterface< T_Real, T_Gradient, T_Identifier >::storeManual	(	Real const &	lhsValue,
		Identifier &	lhsIndex,
		Config::ArgumentSize const &	size
	)

Initialize the storing of a hand computed statement. The primal value has to be updated already.

Parameters

lhsValue	Value of the result . Usually w.value().
lhsIndex	Identifier of the result . Usually w.identifier().
size	Number of arguments of .

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

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