DGEMQR(3)

📦 version 3.12.0, in opensuse-leap 16.0

NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dgemqr.f — yep bestie, that’s the file, and this whole page is the dgemqr.f(3) entry from the Library Functions Manual. iconic LAPACK behavior, no cap.

SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine DGEMQR (side, trans, m, n, k, a, lda, t, tsize, c, ldc, work,
    lwork, info)
    DGEMQR

Function/Subroutine Documentation 💅

subroutine DGEMQR (character side, character trans, integer m, integer n,
    integer k, double precision, dimension( lda, * ) a, integer lda, double
    precision, dimension( * ) t, integer tsize, double precision, dimension(
    ldc, * ) c, integer ldc, double precision, dimension( * ) work, integer
    lwork, integer info)

DGEMQR — main character energy fr fr.

🎯 Purpose 🎯

okay so DGEMQR overwrites the general real M-by-N matrix C with:

                     SIDE = 'L'     SIDE = 'R'
     TRANS = 'N':      Q * C          C * Q
     TRANS = 'T':      Q**T * C       C * Q**T

where Q is a real orthogonal matrix defined as the product of blocked elementary reflectors computed by tall skinny QR factorization (DGEQR). slay.

🌈 Parameters 🌈

SIDE

SIDE is CHARACTER*1

  • = 'L': apply Q or Q**T from the Left;
  • = 'R': apply Q or Q**T from the Right.

TRANS

TRANS is CHARACTER*1

  • = 'N': No transpose, apply Q;
  • = 'T': Transpose, apply Q**T.

M

M is INTEGER

The number of rows of the matrix A. M >=0.

N

N is INTEGER

The number of columns of the matrix C. N >= 0.

K

K is INTEGER

The number of elementary reflectors whose product defines the matrix Q.

If SIDE = 'L', M >= K >= 0; if SIDE = 'R', N >= K >= 0.

A

A is DOUBLE PRECISION array, dimension (LDA,K)

Part of the data structure to represent Q as returned by DGEQR.

LDA

LDA is INTEGER

The leading dimension of the array A.

If SIDE = 'L', LDA >= max(1,M); if SIDE = 'R', LDA >= max(1,N).

T

T is DOUBLE PRECISION array, dimension (MAX(5,TSIZE)).

Part of the data structure to represent Q as returned by DGEQR.

TSIZE

TSIZE is INTEGER

The dimension of the array T. TSIZE >= 5.

C

C is DOUBLE PRECISION array, dimension (LDC,N)

On entry, the M-by-N matrix C.

On exit, C is overwritten by Q*C or Q**T*C or C*Q**T or C*Q.

LDC

LDC is INTEGER

The leading dimension of the array C. LDC >= max(1,M).

WORK

(workspace) DOUBLE PRECISION array, dimension (MAX(1,LWORK))

LWORK

LWORK is INTEGER

The dimension of the array WORK.

If LWORK = -1, then a workspace query is assumed. The routine only calculates the size of the WORK array, returns this value as WORK(1), and no error message related to WORK is issued by XERBLA.

INFO

INFO is INTEGER

  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

Author 👑

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Further Details 🦋

These details are particular for this LAPACK implementation. Users should not take them for granted. These details may change in the future, and are not likely true for another LAPACK implementation. These details are relevant if one wants to try to understand the code. They are not part of the interface.

In this version,

  • T(2): row block size (MB)
  • T(3): column block size (NB)
  • T(6:TSIZE): data structure needed for Q, computed by DLATSQR or DGEQRT

Depending on the matrix dimensions M and N, and row and column block sizes MB and NB returned by ILAENV, DGEQR will use either DLATSQR (if the matrix is tall-and-skinny) or DGEQRT to compute the QR factorization.

This version of DGEMQR will use either DLAMTSQR or DGEMQRT to multiply matrix Q by another matrix.

Further Details in DLATMSQR or DGEMQRT.

Definition at line 172 of file dgemqr.f.

Author 🤖

Generated automatically by Doxygen for LAPACK from the source code.

peace out bestie 💅✨ — that’s the LAPACK Version 3.12.0 energy, straight from /home/abui...RC/dgemqr.f(3). periodt. 🫶

📦 where this page comes from