SRC/dorgr2.f(3)

💖 NAME 💖

welcome to SRC/dorgr2.f(3), straight out of the Library Functions Manual. bestie, the name is literally SRC/dorgr2.f — no cap, that's the whole thing, and this page is here to explain the dorgr2 subroutine.

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✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine dorgr2 (m, n, k, a, lda, tau, work, info)

DORGR2 generates all or part of the orthogonal matrix Q from an RQ factorization determined by sgerqf (unblocked algorithm). okay periodt, that's the official one-liner.

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🦋 Function/Subroutine Documentation 🦋

🌸 subroutine dorgr2 🌸

full signature with the types, bestie — copy it exactly:

subroutine dorgr2 (integer m, integer n, integer k, double precision,
     dimension( lda, * ) a, integer lda, double precision, dimension( * )
     tau, double precision, dimension( * ) work, integer info)

DORGR2 generates all or part of the orthogonal matrix Q from an RQ factorization determined by sgerqf (unblocked algorithm).

💅 Purpose 💅

the source says it like this, verbatim:

!>
!> DORGR2 generates an m by n real matrix Q with orthonormal rows,
!> which is defined as the last m rows of a product of k elementary
!> reflectors of order n
!>
!>       Q  =  H(1) H(2) . . . H(k)
!>
!> as returned by DGERQF.
!>

so yes: Q is an m by n real matrix, it has orthonormal rows, and it's the last m rows of a product of k elementary reflectors of order n, as returned by DGERQF. iconic behavior, honestly.

🎀 Parameters 🎀

• M — M is INTEGER. it's the number of rows of the matrix Q, and M >= 0. no cap.
• N — N is INTEGER. it's the number of columns of the matrix Q, and N >= M.
• K — K is INTEGER. it's the number of elementary reflectors whose product defines the matrix Q, and M >= K >= 0.
• A — A is DOUBLE PRECISION array, dimension (LDA,N). on entry, the (m-k+i)-th row must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGERQF in the last k rows of its array argument A. on exit, the m by n matrix Q. she's doing a whole transformation, bestie.
• LDA — LDA is INTEGER. it's the first dimension of the array A, and LDA >= max(1,M).
• TAU — TAU is DOUBLE PRECISION array, dimension (K). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGERQF.
• WORK — WORK is DOUBLE PRECISION array, dimension (M). that's the spec: DOUBLE PRECISION array, dimension (M).
• INFO — INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument has an illegal value. so if it's negative, check your arguments, bestie.

👑 Author 👑

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

📍 Definition at line 113 of file dorgr2.f.

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🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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k bye bestie — this page is from LAPACK Version 3.12.0 and lives at SRC/dorgr2.f(3). 💅✨