rotg

Computes the parameters for a Givens rotation.

Description

Given the Cartesian coordinates (a, b) of a point, the rotg routines return the parameters c, s, r, and z associated with the Givens rotation. The parameters c and s define a unitary matrix such that:

\[\begin{split}\begin{bmatrix}c & s \\ -s & c\end{bmatrix}. \begin{bmatrix}a \\ b\end{bmatrix} =\begin{bmatrix}r \\ 0\end{bmatrix}\end{split}\]

The parameter z is defined such that if |a| > |b|, z is s; otherwise if c is not 0 z is 1/c; otherwise z is 1.

rotg supports the following precisions.

T	T_res
float	float
double	double
std::complex<float>	float
std::complex<double>	double

rotg (Buffer Version)

Syntax

namespace oneapi::mkl::blas::column_major {
    void rotg(sycl::queue &queue,
              sycl::buffer<T,1> &a,
              sycl::buffer<T,1> &b,
              sycl::buffer<T_real,1> &c,
              sycl::buffer<T,1> &s)
}

namespace oneapi::mkl::blas::row_major {
    void rotg(sycl::queue &queue,
              sycl::buffer<T,1> &a,
              sycl::buffer<T,1> &b,
              sycl::buffer<T_real,1> &c,
              sycl::buffer<T,1> &s)
}

Input Parameters

queue

The queue where the routine should be executed

a

Buffer holding the x-coordinate of the point.

b

Buffer holding the y-coordinate of the point.

Output Parameters

a

Buffer holding the parameter r associated with the Givens rotation.

b

Buffer holding the parameter z associated with the Givens rotation.

c

Buffer holding the parameter c associated with the Givens rotation.

s

Buffer holding the parameter s associated with the Givens rotation.

rotg (USM Version)

Syntax

namespace oneapi::mkl::blas::column_major {
    sycl::event rotg(sycl::queue &queue,
                     T *a,
                     T *b,
                     T_real *c,
                     T *s,
                     const std::vector<sycl::event> &dependencies = {})
}

namespace oneapi::mkl::blas::row_major {
    sycl::event rotg(sycl::queue &queue,
                     T *a,
                     T *b,
                     T_real *c,
                     T *s,
                     const std::vector<sycl::event> &dependencies = {})
}

Input Parameters

queue

The queue where the routine should be executed

a

Pointer to the x-coordinate of the point.

b

Pointer to the y-coordinate of the point.

dependencies

List of events to wait for before starting computation, if any. If omitted, defaults to no dependencies.

Output Parameters

a

Pointer to the parameter r associated with the Givens rotation.

b

Pointer to the parameter z associated with the Givens rotation.

c

Pointer to the parameter c associated with the Givens rotation.

s

Pointer to the parameter s associated with the Givens rotation.

Return Values

Output event to wait on to ensure computation is complete.

Parent topic: BLAS Level 1 Routines