SRC/cunghr.f(3)

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version 3.12.1 · 7 versions
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💖 NAME 💖

okay so this is the Library Functions Manual page for SRC/cunghr.f, bestie 💅 and it's all about CUNGHR and its whole documented crew. no cap, every detail is staying right here. ✨

📜 SYNOPSIS 📜

🧚 Functions/Subroutines 🧚

  • subroutine cunghr (n, ilo, ihi, a, lda, tau, work, lwork, info) — CUNGHR, the main character of this page 👑

🌸 Function/Subroutine Documentation 🌸

✨ subroutine cunghr ✨

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

CUNGHR

🎀 Purpose 🎀

CUNGHR generates a complex unitary matrix Q which is defined as the product of IHI-ILO elementary reflectors of order N, as returned by CGEHRD:

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 CGEHRD. Q is equal to the unit matrix except in the submatrix Q(ilo+1:ihi,ilo+1:ihi). 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.

💜 A

A is COMPLEX array, dimension (LDA,N). On entry, the vectors which define the elementary reflectors, as returned by CGEHRD. On exit, the N-by-N unitary matrix Q.

💜 LDA

LDA is INTEGER. The leading dimension of the array A. LDA >= max(1,N).

💜 TAU

TAU is COMPLEX array, dimension (N-1). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CGEHRD.

💜 WORK

WORK is COMPLEX 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 cunghr.f.

🌈 Author 🌈

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