DORM2R(3)

🎀 DORM2R 🎀

okay bestie, this is the dorm2r.f(3) page from the Library Functions Manual. It’s giving LAPACK, it’s giving unblocked algorithm, and it’s literally about multiplying a general matrix by the orthogonal matrix from a QR factorization determined by sgeqrf. Iconic. 💅

💖 NAME 💖

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dorm2r.f

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

       subroutine DORM2R (side, trans, m, n, k, a, lda, tau, c, ldc, work,
           info)

DORM2R multiplies a general matrix by the orthogonal matrix from a QR factorization determined by sgeqrf (unblocked algorithm).

🫶 Function/Subroutine Documentation 🫶

   subroutine DORM2R (character side, character trans, integer m, integer n,
       integer k, double precision, dimension( lda, * ) a, integer lda, double
       precision, dimension( * ) tau, double precision, dimension( ldc, * ) c,
       integer ldc, double precision, dimension( * ) work, integer info)

DORM2R multiplies a general matrix by the orthogonal matrix from a QR factorization determined by sgeqrf (unblocked algorithm).

✨ Purpose ✨

straight from the source, no cap:

!> DORM2R overwrites the general real m by n matrix C with
!>
!>       Q * C  if SIDE = 'L' and TRANS = 'N', or
!>
!>       Q**T* C  if SIDE = 'L' and TRANS = 'T', or
!>
!>       C * Q  if SIDE = 'R' and TRANS = 'N', or
!>
!>       C * Q**T if SIDE = 'R' and TRANS = 'T',
!>
!> where Q is a real orthogonal matrix defined as the product of k
!> elementary reflectors
!>
!>       Q = H(1) H(2) . . . H(k)
!>
!> as returned by DGEQRF. Q is of order m if SIDE = 'L' and of order n
!> if SIDE = 'R'.

💅 Parameters 💅

• SIDE — CHARACTER*1
  • = 'L': apply Q or Q**T from the Left
  • = 'R': apply Q or Q**T from the Right
• TRANS — CHARACTER*1
  • = 'N': apply Q (No transpose)
  • = 'T': apply Q**T (Transpose)
• M — INTEGER; the number of rows of the matrix C. M >= 0.
• N — INTEGER; the number of columns of the matrix C. N >= 0.
• K — 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 — DOUBLE PRECISION array, dimension (LDA,K). The i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGEQRF in the first k columns of its array argument A. A is modified by the routine but restored on exit.
• LDA — INTEGER; the leading dimension of the array A. If SIDE = 'L', LDA >= max(1,M); if SIDE = 'R', LDA >= max(1,N).
• TAU — DOUBLE PRECISION array, dimension (K). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGEQRF.
• C — 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 — INTEGER; the leading dimension of the array C. LDC >= max(1,M).
• WORK — DOUBLE PRECISION array, dimension (N) if SIDE = 'L', (M) if SIDE = 'R'.
• INFO — 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.

Definition at line 157 of file dorm2r.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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💖 Cute sign-off: LAPACK Version 3.12.0 and /home/abui...RC/dorm2r.f(3) — no date in this footer, so no invented date, bestie; love u, bye! 💖