?rotm

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 3/31/2023

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?rotm

Performs modified Givens rotation of points in the plane.

Syntax

call srotm(n, x, incx, y, incy, param)

call drotm(n, x, incx, y, incy, param)

call rotm(x, y, param)

Include Files

mkl.fi, blas.f90

Description

Given two vectors x and y, each vector element of these vectors is replaced as follows:

for i=1 to n, where H is a modified Givens transformation matrix whose values are stored in the param(2) through param(5) array. See discussion on the param argument.

Input Parameters

n

INTEGER. Specifies the number of elements in vectors x and y.

x

REAL for srotm

DOUBLE PRECISION for drotm

Array, size at least (1 + (n -1)*abs(incx)).

incx

INTEGER. Specifies the increment for the elements of x.

y

REAL for srotm

DOUBLE PRECISION for drotm

Array, size at least (1 + (n -1)*abs(incy)).

incy

INTEGER. Specifies the increment for the elements of y.

param

REAL for srotm

DOUBLE PRECISION for drotm

Array, size 5.

The elements of the param array are:

param(1) contains a switch, flag. param(2-5) contain h₁₁, h₂₁, h₁₂, and h₂₂, respectively, the components of the array H.

Depending on the values of flag, the components of H are set as follows:

flag = -1.0:

flag = 0.0:

flag = 1.0:

flag = -2.0:

In the last three cases, the matrix entries of 1.0, -1.0, and 0.0 are assumed based on the value of flag and are not required to be set in the param vector.

Output Parameters

x: Each element x(i) is replaced by h₁₁*x(i) + h₁₂*y(i).
y: Each element y(i) is replaced by h₂₁*x(i) + h₂₂*y(i).

BLAS 95 Interface Notes

Routines in Fortran 95 interface have fewer arguments in the calling sequence than their FORTRAN 77 counterparts. For general conventions applied to skip redundant or reconstructible arguments, see BLAS 95 Interface Conventions.

Specific details for the routine rotm interface are the following:

x: Holds the vector with the number of elements n.
y: Holds the vector with the number of elements n.

Parent topic: BLAS Level 1 Routines and Functions

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?rotm