BLAS/SRC/drotm.f(3)

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💅 BLAS/SRC/drotm.f 💅

This page comes from the Library Functions Manual, and it is literally all about BLAS/SRC/drotm.f, bestie. Group chat, but for BLAS. 🫶

✨ NAME ✨

BLAS/SRC/drotm.f

🌸 SYNOPSIS 🌸

Functions/Subroutines

subroutine drotm (n, dx, incx, dy, incy, dparam)
    DROTM

🦋 Function/Subroutine Documentation 🦋

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

🎯 Purpose 🎯

Okay so the Purpose is: apply the modified Givens transformation, H, to the 2 by N matrix — and the source lays the matrix out like this, no cap:

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

Then the indexing tea is:

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).

And yeah: SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM. 👑

🧸 Parameters 🧸

  • N — N is INTEGER; it’s the number of elements in input vector(s). 💖
  • DX — DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) ). 🦋
  • INCX — INCX is INTEGER; it’s the storage spacing between elements of DX. ✨
  • DY — DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) ). 🎀
  • INCY — INCY is INTEGER; it’s the storage spacing between elements of DY. 💅
  • DPARAM — DPARAM is DOUBLE PRECISION array, dimension (5), and the mapping is:
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.

Definition at line 95 of file drotm.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

Alright bestie, that’s the whole page 💖 signed off from LAPACK, Version 3.12.0, with the footer marker BLAS/SRC/drotm.f(3) — that’s the date/footer bit on this page, iykyk. Byeee 🫶

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