sleipnir::detail::Expression Struct Reference

An autodiff expression node. More...

#include </home/runner/work/allwpilib/allwpilib/wpimath/src/main/native/thirdparty/sleipnir/include/sleipnir/autodiff/Expression.hpp>

Public Types
using	BinaryFuncDouble = double (*)(double, double)
	Binary function taking two doubles and returning a double.
using	TrinaryFuncDouble = double (*)(double, double, double)
	Trinary function taking three doubles and returning a double.
using	TrinaryFuncExpr
	Trinary function taking three expressions and returning an expression.

Public Member Functions
constexpr	Expression ()=default
	Constructs a constant expression with a value of zero.
constexpr	Expression (double value, ExpressionType type=ExpressionType::kConstant)
	Constructs a nullary expression (an operator with no arguments).
constexpr	Expression (ExpressionType type, BinaryFuncDouble valueFunc, TrinaryFuncDouble lhsGradientValueFunc, TrinaryFuncExpr lhsGradientFunc, ExpressionPtr lhs)
	Constructs an unary expression (an operator with one argument).
constexpr	Expression (ExpressionType type, BinaryFuncDouble valueFunc, TrinaryFuncDouble lhsGradientValueFunc, TrinaryFuncDouble rhsGradientValueFunc, TrinaryFuncExpr lhsGradientFunc, TrinaryFuncExpr rhsGradientFunc, ExpressionPtr lhs, ExpressionPtr rhs)
	Constructs a binary expression (an operator with two arguments).
constexpr bool	IsConstant (double constant) const
	Returns true if the expression is the given constant.

Public Attributes
double	value = 0.0
	The value of the expression node.
double	adjoint = 0.0
	The adjoint of the expression node used during autodiff.
uint32_t	duplications = 0
	Tracks the number of instances of this expression yet to be encountered in an expression tree.
int32_t	row = -1
	This expression's row in wrt for autodiff gradient, Jacobian, or Hessian.
ExpressionPtr	adjointExpr
	The adjoint of the expression node used during gradient expression tree generation.
ExpressionType	type = ExpressionType::kConstant
	Expression argument type.
uint32_t	refCount = 0
	Reference count for intrusive shared pointer.
BinaryFuncDouble	valueFunc = nullptr
	Either nullary operator with no arguments, unary operator with one argument, or binary operator with two arguments.
std::array< TrinaryFuncDouble, 2 >	gradientValueFuncs {nullptr, nullptr}
	Functions returning double adjoints of the children expressions.
std::array< TrinaryFuncExpr, 2 >	gradientFuncs {nullptr, nullptr}
	Functions returning Variable adjoints of the children expressions.
std::array< ExpressionPtr, 2 >	args {nullptr, nullptr}
	Expression arguments.

Friends
SLEIPNIR_DLLEXPORT ExpressionPtr	operator* (const ExpressionPtr &lhs, const ExpressionPtr &rhs)
	Expression-Expression multiplication operator.
SLEIPNIR_DLLEXPORT ExpressionPtr	operator/ (const ExpressionPtr &lhs, const ExpressionPtr &rhs)
	Expression-Expression division operator.
SLEIPNIR_DLLEXPORT ExpressionPtr	operator+ (const ExpressionPtr &lhs, const ExpressionPtr &rhs)
	Expression-Expression addition operator.
SLEIPNIR_DLLEXPORT ExpressionPtr	operator- (const ExpressionPtr &lhs, const ExpressionPtr &rhs)
	Expression-Expression subtraction operator.
SLEIPNIR_DLLEXPORT ExpressionPtr	operator- (const ExpressionPtr &lhs)
	Unary minus operator.
SLEIPNIR_DLLEXPORT ExpressionPtr	operator+ (const ExpressionPtr &lhs)
	Unary plus operator.

Detailed Description

An autodiff expression node.

Member Typedef Documentation

BinaryFuncDouble

using sleipnir::detail::Expression::BinaryFuncDouble = double (*)(double, double)

Binary function taking two doubles and returning a double.

TrinaryFuncDouble

using sleipnir::detail::Expression::TrinaryFuncDouble = double (*)(double, double, double)

Trinary function taking three doubles and returning a double.

TrinaryFuncExpr

using sleipnir::detail::Expression::TrinaryFuncExpr

Initial value:

 ExpressionPtr (*)(const ExpressionPtr&,
                                            const ExpressionPtr&,
                                            const ExpressionPtr&)

Trinary function taking three expressions and returning an expression.

Constructor & Destructor Documentation

Expression() [1/4]

sleipnir::detail::Expression::Expression ( )

constexprdefault

Constructs a constant expression with a value of zero.

Expression() [2/4]

sleipnir::detail::Expression::Expression ( double value, ExpressionType type = ExpressionType::kConstant )

inlineexplicitconstexpr

Constructs a nullary expression (an operator with no arguments).

Parameters

value	The expression value.
type	The expression type. It should be either constant (the default) or linear.

Expression() [3/4]

sleipnir::detail::Expression::Expression ( ExpressionType type, BinaryFuncDouble valueFunc, TrinaryFuncDouble lhsGradientValueFunc, TrinaryFuncExpr lhsGradientFunc, ExpressionPtr lhs )

inlineconstexpr

Constructs an unary expression (an operator with one argument).

Parameters

type	The expression's type.
valueFunc	Unary operator that produces this expression's value.
lhsGradientValueFunc	Gradient with respect to the operand.
lhsGradientFunc	Gradient with respect to the operand.
lhs	Unary operator's operand.

Expression() [4/4]

sleipnir::detail::Expression::Expression ( ExpressionType type, BinaryFuncDouble valueFunc, TrinaryFuncDouble lhsGradientValueFunc, TrinaryFuncDouble rhsGradientValueFunc, TrinaryFuncExpr lhsGradientFunc, TrinaryFuncExpr rhsGradientFunc, ExpressionPtr lhs, ExpressionPtr rhs )

inlineconstexpr

Constructs a binary expression (an operator with two arguments).

Parameters

type	The expression's type.
valueFunc	Unary operator that produces this expression's value.
lhsGradientValueFunc	Gradient with respect to the left operand.
rhsGradientValueFunc	Gradient with respect to the right operand.
lhsGradientFunc	Gradient with respect to the left operand.
rhsGradientFunc	Gradient with respect to the right operand.
lhs	Binary operator's left operand.
rhs	Binary operator's right operand.

Member Function Documentation

IsConstant()

bool sleipnir::detail::Expression::IsConstant ( double constant ) const

inlineconstexpr

Returns true if the expression is the given constant.

Parameters

constant

The constant.

Friends And Related Symbol Documentation

operator*

SLEIPNIR_DLLEXPORT ExpressionPtr operator* ( const ExpressionPtr & lhs, const ExpressionPtr & rhs )

friend

Expression-Expression multiplication operator.

Parameters

lhs	Operator left-hand side.
rhs	Operator right-hand side.

operator+ [1/2]

SLEIPNIR_DLLEXPORT ExpressionPtr operator+ ( const ExpressionPtr & lhs )

friend

Unary plus operator.

Parameters

lhs	Operand of unary plus.

operator+ [2/2]

SLEIPNIR_DLLEXPORT ExpressionPtr operator+ ( const ExpressionPtr & lhs, const ExpressionPtr & rhs )

friend

Expression-Expression addition operator.

Parameters

lhs	Operator left-hand side.
rhs	Operator right-hand side.

operator- [1/2]

SLEIPNIR_DLLEXPORT ExpressionPtr operator- ( const ExpressionPtr & lhs )

friend

Unary minus operator.

Parameters

lhs	Operand of unary minus.

operator- [2/2]

SLEIPNIR_DLLEXPORT ExpressionPtr operator- ( const ExpressionPtr & lhs, const ExpressionPtr & rhs )

friend

Expression-Expression subtraction operator.

Parameters

lhs	Operator left-hand side.
rhs	Operator right-hand side.

operator/

SLEIPNIR_DLLEXPORT ExpressionPtr operator/ ( const ExpressionPtr & lhs, const ExpressionPtr & rhs )

friend

Expression-Expression division operator.

Parameters

lhs	Operator left-hand side.
rhs	Operator right-hand side.

Member Data Documentation

adjoint

double sleipnir::detail::Expression::adjoint = 0.0

The adjoint of the expression node used during autodiff.

adjointExpr

ExpressionPtr sleipnir::detail::Expression::adjointExpr

The adjoint of the expression node used during gradient expression tree generation.

args

std::array<ExpressionPtr, 2> sleipnir::detail::Expression::args {nullptr, nullptr}

Expression arguments.

duplications

uint32_t sleipnir::detail::Expression::duplications = 0

Tracks the number of instances of this expression yet to be encountered in an expression tree.

gradientFuncs

std::array<TrinaryFuncExpr, 2> sleipnir::detail::Expression::gradientFuncs {nullptr, nullptr}

Functions returning Variable adjoints of the children expressions.

Parameters:

• lhs: Left argument to binary operator.
• rhs: Right argument to binary operator.
• parentAdjoint: Adjoint of parent expression.

gradientValueFuncs

std::array<TrinaryFuncDouble, 2> sleipnir::detail::Expression::gradientValueFuncs {nullptr, nullptr}

Functions returning double adjoints of the children expressions.

Parameters:

• lhs: Left argument to binary operator.
• rhs: Right argument to binary operator.
• parentAdjoint: Adjoint of parent expression.

refCount

uint32_t sleipnir::detail::Expression::refCount = 0

Reference count for intrusive shared pointer.

row

int32_t sleipnir::detail::Expression::row = -1

This expression's row in wrt for autodiff gradient, Jacobian, or Hessian.

This is -1 if the expression isn't in wrt.

type

ExpressionType sleipnir::detail::Expression::type = ExpressionType::kConstant

Expression argument type.

value

double sleipnir::detail::Expression::value = 0.0

The value of the expression node.

valueFunc

BinaryFuncDouble sleipnir::detail::Expression::valueFunc = nullptr

Either nullary operator with no arguments, unary operator with one argument, or binary operator with two arguments.

This operator is used to update the node's value.

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

• /home/runner/work/allwpilib/allwpilib/wpimath/src/main/native/thirdparty/sleipnir/include/sleipnir/autodiff/Expression.hpp