BLAS 1::rotmg

KokkosBlas::rotmg()

Header File: KokkosBlas1_rotmg.hpp

Usage: KokkosBlas::rotmg(space, d1, d2, x1, y1, params); KokkosBlas::rotmg(d1, d2, x1, y1, params);

Computes the modified Givens rotation coefficients that zeroes out the second entry of vector (sqrt(d1)*x1, sqrt(d2)*y1). The flag flag=params(0) dictates the structure of the matrix H

flag=-1.0	flag= 0.0	flag= 1.0	flag=-2.0
[h11 h12]	[1.0 h12]	[h11 1.0]	[1.0 0.0]
[h21 h22]	[h21 1.0]	[-1. h12]	[0.0 1.0]

Note that the values -1.0, 0.0 and 1.0 implied by the flag are not stored in params.

Interface

template <class execution_space, class DXView, class YView, class PView>
void rotmg(execution_space const& space, DXView const& d1, DXView const& d2,
           DXView const& x1, YView const& y1, PView const& param)

template <class DXView, class YView, class PView>
void rotmg(DXView const& d1, DXView const& d2, DXView const& x1,
           YView const& y1, PView const& param)

Template parameters:

• execution_space: the backend that will be used to run this kernel
• DXView: the type of the input views d1, d2 and x1
• YView: the type of the input view y1
• PView: the type of the params input

Parameters:

• space: the execution space instance passed to the Kokkos execution policy to run the kernel on
• d1: Input, first scaling factor
• d2: Input, second scaling factor
• x1: Input, first component of the vector to rotate
• y1: Input, second component of the vector to rotate
• params: the params(0) is the control flag and params(1:4) are the coefficients of the rotation matrix H

Example