SRC/dgeqrt2.f(3)

✨ SRC/dgeqrt2.f ✨

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🌸 NAME 🌸

SRC/dgeqrt2.f

That's the name, no notes, no extras. 🎀

✨ SYNOPSIS ✨

💖 Functions/Subroutines 💖

• subroutine dgeqrt2 (m, n, a, lda, t, ldt, info) — DGEQRT2 computes a QR factorization of a general real or complex matrix using the compact WY representation of Q.

💅 Function/Subroutine Documentation 💅

🫶 subroutine dgeqrt2 🫶

okay so here's the full signature, character for character:

subroutine dgeqrt2 (integer m, integer n, double precision, dimension( lda,
* ) a, integer lda, double precision, dimension( ldt, * ) t, integer
ldt, integer info)

DGEQRT2 computes a QR factorization of a general real or complex matrix using the compact WY representation of Q. periodt. 🔥

🎀 Purpose 🎀

DGEQRT2 computes a QR factorization of a real M-by-N matrix A, using the compact WY representation of Q. That's the whole vibe. ✨

🫶 Parameters 🫶

• M — M is INTEGER. The number of rows of the matrix A. M >= N.
• N — N is INTEGER. The number of columns of the matrix A. N >= 0.
• A — A is DOUBLE PRECISION array, dimension (LDA,N). On entry, the real M-by-N matrix A. On exit, the elements on and above the diagonal contain the N-by-N upper triangular matrix R; the elements below the diagonal are the columns of V. See below for further details. 👀
• LDA — LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,M).
• T — T is DOUBLE PRECISION array, dimension (LDT,N). The N-by-N upper triangular factor of the block reflector. The elements on and above the diagonal contain the block reflector T; the elements below the diagonal are not used. See below for further details.
• LDT — LDT is INTEGER. The leading dimension of the array T. LDT >= max(1,N).
• INFO — INFO is INTEGER. = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value.

👑 Author 👑

The academic icons behind this:

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

🔍 Further Details 🔍

The matrix V stores the elementary reflectors H(i) in the i-th column below the diagonal. For example, if M=5 and N=3, the matrix V is:

               V = (  1       )
                   ( v1  1    )
                   ( v1 v2  1 )
                   ( v1 v2 v3 )
                   ( v1 v2 v3 )

where the vi's represent the vectors which define H(i), which are returned in the matrix A. The 1's along the diagonal of V are not stored in A. The block reflector H is then given by

               H = I - V * T * V**T

where V**T is the transpose of V. no cap, that transpose is doing its thing. 💜

Definition at line 126 of file dgeqrt2.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

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