cg_impls.h File Reference

Headers for function prototypes and typedefs. More...

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Typedefs
typedef void(*	Aop) (void *, int, const double *, int, double *, int)
	The prototype of all matrix-vector operators. It requires six parameters and has no return value. More...

Functions
int	rb_dcgsv (int, Aop, void *, const double *, double *)
	Solves a linear system using conjugate method. More...
void	rb_dscal (int, double, double *, int)
	Scales a vector by a constant. . More...
void	rb_daxpy (int, double, const double *, int, double *, int)
	Scale a vector X by a constant add add it to another vector Y. . More...
double	rb_damax (int, const double *, int)
	Finds the element in X which has the maximum absolute value. More...
double	rb_ddot (int, const double *, int, const double *, int)
	Perform inner product . More...
void	rb_dsub (int, const double *, int, const double *, int, double *, int)
	Perform vector substraction, i.e. . More...
void	rb_dcopy (int, const double *, int, double *, int)
	Copy a vector to another. More...

Detailed Description

Headers for function prototypes and typedefs.

Typedef Documentation

typedef void(* Aop)(void *, int, const double *, int, double *, int)

The prototype of all matrix-vector operators. It requires six parameters and has no return value.

Parameters

ctxt	Type void*. All necessary contexts needed by the operator.
n	Type int. the length of X and Y.
X	Type const double*. The pointer to the storage of X.
incx	Type int. The increment of indices of X.
Y	Type double*. Input/Output. The pointer to the storage of Y.
incy	Type int. The increment of indices of Y.

Function Documentation

double rb_damax	(	int	n,
		const double *	X,
		int	incx
	)

Finds the element in X which has the maximum absolute value.

Parameters

n	The length of X.
X	The pointer to the storage of X.
incx	The increment of indices of X.

Returns

The element which has the maximum absolute value

void rb_daxpy	(	int	n,
		double	a,
		const double *	X,
		int	incx,
		double *	Y,
		int	incy
	)

Scale a vector X by a constant add add it to another vector Y. .

Parameters

n	The length of X and Y.
a	The scaling constant.
X	The pointer to the storage of X.
incx	The increment of indices of X.
Y	Input/Output. The pointer to the storage of Y.
incy	The increment of indices of Y.

int rb_dcgsv	(	int	n,
		Aop	A,
		void *	ctxt,
		const double *	b,
		double *	sol
	)

Solves a linear system using conjugate method.

Parameters

n	The dimension of A.
A	The function pointer of type Aop.
ctxt	The context needed by A.
b	The right hand side of .
sol	Output. The computed solution of the equation.

Returns

The number of iterations in the conjugate method.

The function rb_dcgsv solves the linear system with conjugate gradient method. It requires to be positive definite.

Conjugate gradient method doesn't need the matrix to be given explicitly. It only needs when applying it to a vector. That is, the user only has to tell how to perform , by providing the parameter of type Aop and all the context needed by the operator.

void rb_dcopy	(	int	n,
		const double *	X,
		int	incx,
		double *	Y,
		int	incy
	)

Copy a vector to another.

Parameters

n	The length of X and Y.
X	The pointer to the storage of X.
incx	The increment of indices of X.
Y	The pointer to the storage of Y.
incy	The increment of indices of Y.

double rb_ddot	(	int	n,
		const double *	X,
		int	incx,
		const double *	Y,
		int	incy
	)

Perform inner product .

Parameters

n	The length of X and Y.
X	The pointer to the storage of X.
incx	The increment of indices of X.
Y	The pointer to the storage of Y.
incy	The increment of indices of Y.

Returns

The inner product.

void rb_dscal	(	int	n,
		double	a,
		double *	X,
		int	incx
	)

Scales a vector by a constant. .

Parameters

n	The length of X.
a	The scaling factor.
X	The pointer to the storage of X.
incx	The increment of indices.

void rb_dsub	(	int	n,
		const double *	X,
		int	incx,
		const double *	Y,
		int	incy,
		double *	Z,
		int	incz
	)

Perform vector substraction, i.e. .

Parameters

n	The length of X and Y.
X	The pointer to the storage of X.
incx	The increment of indices of X.
Y	The pointer to the storage of Y.
incy	The increment of indices of Y.
Z	Output. The pointer to the storage of Z.
incy	The increment of indices of Z.