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rotm(3) LAPACK rotm(3)

NAME

rotm - rotm: apply modified (fast) plane rotation

SYNOPSIS

Functions


subroutine drotm (n, dx, incx, dy, incy, dparam)
DROTM subroutine srotm (n, sx, incx, sy, incy, sparam)
SROTM

Detailed Description

Function Documentation

subroutine drotm (integer n, double precision, dimension(*) dx, integer incx, double precision, dimension(*) dy, integer incy, double precision, dimension(5) dparam)

DROTM

Purpose:



    APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX


    (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN


    (DY**T)


    DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE


    LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY.


    WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..


    DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0


      (DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0)


    H=(          )    (          )    (          )    (          )


      (DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0).


    SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM.

Parameters

N 



          N is INTEGER


         number of elements in input vector(s)

DX



          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )

INCX



          INCX is INTEGER


         storage spacing between elements of DX

DY



          DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )

INCY



          INCY is INTEGER


         storage spacing between elements of DY

DPARAM



          DPARAM is DOUBLE PRECISION array, dimension (5)


     DPARAM(1)=DFLAG


     DPARAM(2)=DH11


     DPARAM(3)=DH21


     DPARAM(4)=DH12


     DPARAM(5)=DH22

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

subroutine srotm (integer n, real, dimension(*) sx, integer incx, real, dimension(*) sy, integer incy, real, dimension(5) sparam)

SROTM

Purpose:



    APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX


    (SX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF SX ARE IN


    (SX**T)


    SX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE


    LX = (-INCX)*N, AND SIMILARLY FOR SY USING USING LY AND INCY.


    WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..


    SFLAG=-1.E0     SFLAG=0.E0        SFLAG=1.E0     SFLAG=-2.E0


      (SH11  SH12)    (1.E0  SH12)    (SH11  1.E0)    (1.E0  0.E0)


    H=(          )    (          )    (          )    (          )


      (SH21  SH22),   (SH21  1.E0),   (-1.E0 SH22),   (0.E0  1.E0).


    SEE  SROTMG FOR A DESCRIPTION OF DATA STORAGE IN SPARAM.

Parameters

N 



          N is INTEGER


         number of elements in input vector(s)

SX



          SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )

INCX



          INCX is INTEGER


         storage spacing between elements of SX

SY



          SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) )

INCY



          INCY is INTEGER


         storage spacing between elements of SY

SPARAM



          SPARAM is REAL array, dimension (5)


     SPARAM(1)=SFLAG


     SPARAM(2)=SH11


     SPARAM(3)=SH21


     SPARAM(4)=SH12


     SPARAM(5)=SH22

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Author

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Wed Feb 7 2024 11:30:40 Version 3.12.0