DORMHR(3)

🦋 DORMHR(3) — Library Functions Manual 🦋

🌸 NAME 🌸

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dormhr.f — yes bestie, that's the source file this whole page is about. It's DORMHR, and we're gonna get into it. ✨

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine DORMHR (side, trans, m, n, ilo, ihi, a, lda, tau, c, ldc,
    work, lwork, info)

DORMHR — the main character, literally.

🛠️ Function/Subroutine Documentation 🛠️

subroutine DORMHR (character side, character trans, integer m, integer n,
    integer ilo, integer ihi, double precision, dimension( lda, * ) a,
    integer lda, double precision, dimension( * ) tau, double precision,
    dimension( ldc, * ) c, integer ldc, double precision, dimension( * )
    work, integer lwork, integer info)

DORMHR — iconic signature behavior, no notes.

🎯 Purpose 🎯

DORMHR 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 of order nq, with nq = m if SIDE = 'L' and nq = n if SIDE = 'R'. Q is defined as the product of IHI-ILO elementary reflectors, as returned by DGEHRD:

Q = H(ilo) H(ilo+1) . . . H(ihi-1).

That's the whole vibe of what she does, bestie. 💅

💖 Parameters 💖

All the deets, no gatekeeping:

• SIDE — SIDE is CHARACTER*1; = 'L': apply Q or Q**T from the Left; = 'R': apply Q or Q**T from the Right. Pick a side, bestie.
• 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 C. M >= 0.
• N — N is INTEGER; the number of columns of the matrix C. N >= 0.
• ILO — ILO is INTEGER.
• IHI — IHI is INTEGER. ILO and IHI must have the same values as in the previous call of DGEHRD. Q is equal to the unit matrix except in the submatrix Q(ilo+1:ihi,ilo+1:ihi). If SIDE = 'L', then 1 <= ILO <= IHI <= M, if M > 0, and ILO = 1 and IHI = 0, if M = 0; if SIDE = 'R', then 1 <= ILO <= IHI <= N, if N > 0, and ILO = 1 and IHI = 0, if N = 0. Do not freestyle these bounds.
• A — A is DOUBLE PRECISION array, dimension (LDA,M) if SIDE = 'L', (LDA,N) if SIDE = 'R'; the vectors which define the elementary reflectors, as returned by DGEHRD.
• LDA — LDA is INTEGER; the leading dimension of the array A. LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.
• TAU — TAU is DOUBLE PRECISION array, dimension (M-1) if SIDE = 'L', (N-1) if SIDE = 'R'; TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGEHRD.
• 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. She gets rewritten, periodt.
• LDC — LDC is INTEGER; the leading dimension of the array C. LDC >= max(1,M).
• WORK — WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
• LWORK — LWORK is INTEGER; the dimension of the array WORK. If SIDE = 'L', LWORK >= max(1,N); if SIDE = 'R', LWORK >= max(1,M). For optimum performance LWORK >= N*NB if SIDE = 'L', and LWORK >= M*NB if SIDE = 'R', where NB is the optimal blocksize. If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA. Workspace query era.
• 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.

Definition at line 176 of file dormhr.f.

👑 Author 👑

Generated automatically by Doxygen for LAPACK from the source code.

---

That's the whole page, bestie! Source/version vibes: LAPACK Version 3.12.0, generated from the source code, with the footer's truncated path /home/abui...RC/dormhr.f(3) — and no date on that footer line, just so you know. 💖🎀✨