DOPMTR(3)

🦋 DOPMTR(3) — bestie, it's the packed-reflector apply routine 🦋

okay so this page lives at /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/dopmtr.f — that's the NAME bit, bestie, that whole entire path is literally the name of this page 💅 and yes it's from the LAPACK Library Functions Manual, we love a glow-up 🎀

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✨ SYNOPSIS ✨

Functions/Subroutines

subroutine DOPMTR (side, uplo, trans, m, n, ap, tau, c, ldc, work, info)

DOPMTR — that's the whole vibe, no cap 🫶

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🌸 Function/Subroutine Documentation 🌸

subroutine DOPMTR (character side, character uplo, character trans, integer
    m, integer n, double precision, dimension( * ) ap, double precision,
    dimension( * ) tau, double precision, dimension( ldc, * ) c, integer
    ldc, double precision, dimension( * ) work, integer info)

DOPMTR ✨ (again, iconic, we stan a self-titled moment)

💖 Purpose:

okay so here's the tea, bestie — DOPMTR 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 nq-1 elementary reflectors, as returned by DSPTRD using packed storage 🌈:

• if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);
• if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).

like, it's giving "I'm just gonna quietly replace your matrix and then leave" 😭 main character energy fr fr

🎀 Parameters

• SIDE — SIDE is CHARACTER*1 💅
  • = 'L': apply Q or Q**T from the Left;
  • = 'R': apply Q or Q**T from the Right.
• UPLO — UPLO is CHARACTER*1 🦋
  • = 'U': Upper triangular packed storage used in previous call to DSPTRD;
  • = 'L': Lower triangular packed storage used in previous call to DSPTRD.
• 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.
• AP — AP is DOUBLE PRECISION array, dimension
  • (M*(M+1)/2) if SIDE = 'L'
  • (N*(N+1)/2) if SIDE = 'R'

The vectors which define the elementary reflectors, as returned by DSPTRD. AP is modified by the routine but restored on exit. (so like, it goes out, has a little adventure, comes back exactly the same — we love a routine that puts things back where it found them 🫶)

• TAU — TAU is DOUBLE PRECISION array, dimension (M-1) if SIDE = 'L' or (N-1) if SIDE = 'R' 💜
  • TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DSPTRD.
• 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's been transformed, she's a whole new woman 💅)
• LDC — LDC is INTEGER 👑
  • The leading dimension of the array C. LDC >= max(1,M).
• WORK — WORK is DOUBLE PRECISION array, dimension
  • (N) if SIDE = 'L'
  • (M) if SIDE = 'R'
• 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

Definition at line 148 of file dopmtr.f.

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🌈 Author

Generated automatically by Doxygen for LAPACK from the source code. (yes bestie, a robot wrote it, and honestly? it ate 🙈)

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okay so that's the whole page 💖 cute little sign-off time: this was LAPACK, Version 3.12.0, and the file is /home/abui...RC/dopmtr.f(3) — go forth and apply those reflectors, bestie, you've got this 🧚🎀💜