SRC/sorghr.f(3)

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version 3.12.1 · 7 versions
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💖 NAME 💖

SRC/sorghr.f — the page for the SORGHR subroutine, periodt 💅

Okay so this is the SRC/sorghr.f(3) page from the Library Functions Manual, and it is lowkey all about one very specific LAPACK baddie: SORGHR ✨

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine sorghr (n, ilo, ihi, a, lda, tau, work, lwork, info)
    SORGHR

🦋 Function/Subroutine Documentation 🦋

subroutine sorghr (integer n, integer ilo, integer ihi, real, dimension(
     lda, * ) a, integer lda, real, dimension( * ) tau, real, dimension( * )
     work, integer lwork, integer info)

SORGHR 💫

🎀 Purpose 🎀

SORGHR generates a real orthogonal matrix Q which is defined as the product of IHI-ILO elementary reflectors of order N, as returned by SGEHRD:

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

🍓 Parameters 🍓

  • N — N is INTEGER; the order of the matrix Q. N >= 0 👑
  • ILO — ILO is INTEGER 🫶
  • IHI — IHI is INTEGER; ILO and IHI must have the same values as in the previous call of SGEHRD. Q is equal to the unit matrix except in the submatrix Q(ilo+1:ihi,ilo+1:ihi). Also: 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
  • A — A is REAL array, dimension (LDA,N). On entry, the vectors which define the elementary reflectors, as returned by SGEHRD. On exit, the N-by-N orthogonal matrix Q 🌈
  • LDA — LDA is INTEGER; the leading dimension of the array A. LDA >= max(1,N).
  • TAU — TAU is REAL array, dimension (N-1). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SGEHRD 🎀
  • WORK — WORK is REAL 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. LWORK >= IHI-ILO. For optimum performance LWORK >= (IHI-ILO)*NB, 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 😭

  • 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 125 of file sorghr.f.

👑 Author 👑

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Later, bestie! This adorable page is brought to you by LAPACK, Version 3.12.0, and its home is SRC/sorghr.f(3) 🫶✨

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