Function

cblas_drotg

Constructs a Givens rotation matrix.

Declaration

void cblas_drotg(double *__a, double *__b, double *__c, double *__s);

Parameters

a

Double-precision value a. Overwritten on return with result r.

b

Double-precision value b. Overwritten on return with result z (zero).

c

Unused on entry. Overwritten on return with the value cos(θ).

s

Unused on entry. Overwritten on return with the value sin(θ).

Discussion

Given a vertical matrix containing a and b, computes the values of cos θ and sin θ that zero the lower value (b). Returns the value of sin θ in s, the value of cos θ in c, and the upper value (r) in a.

See Also

Double-Precision Float Matrix Functions

cblas_dasum

Computes the sum of the absolute values of elements in a vector (double-precision).

cblas_daxpy

Computes a constant times a vector plus a vector (double-precision).

cblas_dcopy

Copies a vector to another vector (double-precision).

cblas_dgbmv

Scales a general band matrix, then multiplies by a vector, then adds a vector (double precision).

cblas_dgemm

Multiplies two matrices (double-precision).

cblas_dgemv

Multiplies a matrix by a vector (double precision).

cblas_dger

Multiplies vector X by the transpose of vector Y, then adds matrix A (double precison).

cblas_dnrm2

Computes the L2 norm (Euclidian length) of a vector (double precision).

cblas_drot

Applies a Givens rotation matrix to a pair of vectors.

cblas_drotm

Applies a modified Givens transformation (single precision).

cblas_drotmg

Generates a modified Givens rotation matrix.

cblas_dsbmv

Scales a symmetric band matrix, then multiplies by a vector, then adds a vector (double precision).

cblas_dscal

Multiplies each element of a vector by a constant (double-precision).

cblas_dspmv

Scales a packed symmetric matrix, then multiplies by a vector, then scales and adds another vector (double precision).

cblas_dspr

Rank one update: adds a packed symmetric matrix to the product of a scaling factor, a vector, and its transpose (double precision).

cblas_dspr2

Rank two update of a packed symmetric matrix using two vectors (single precision).

cblas_dswap

Exchanges the elements of two vectors (double precision).

cblas_dsymm

Multiplies a matrix by a symmetric matrix (double-precision).

cblas_dsymv

Scales a symmetric matrix, multiplies by a vector, then scales and adds another vector (single precision).

cblas_dsyr

Rank one update: adds a symmetric matrix to the product of a scaling factor, a vector, and its transpose (double precision).

cblas_dsyr2

Rank two update of a symmetric matrix using two vectors (single precision).

cblas_dsyr2k

Performs a rank-2k update of a symmetric matrix (double precision).

cblas_dsyrk

Rank-k update—multiplies a symmetric matrix by its transpose and adds a second matrix (double precision).

cblas_dtbmv

Scales a triangular band matrix, then multiplies by a vector (double precision).

cblas_dtbsv

Solves a triangular banded system of equations.

cblas_dtpmv

Multiplies a triangular matrix by a vector, then adds a vector (double precision).

cblas_dtpsv

Solves a packed triangular system of equations.

cblas_dtrmm

Scales a triangular matrix and multiplies it by a matrix.

cblas_dtrmv

Multiplies a triangular matrix by a vector.

cblas_dtrsm

Solves a triangular system of equations with multiple values for the right side.

cblas_dtrsv

Solves a triangular system of equations with a single value for the right side.