SRC/zungqr.f(3)

📦
version 3.12.1 · 7 versions
, in arch rolling

🌸 NAME 🌸

okay so this is SRC/zungqr.f(3) from the Library Functions Manual, and the NAME on the tin is literally SRC/zungqr.f. bestie, we are deep in LAPACK land and the routine is ZUNGQR 💅

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

   Functions/Subroutines
       subroutine zungqr (m, n, k, a, lda, tau, work, lwork, info)
           ZUNGQR

🫶 Function/Subroutine Documentation 🫶

   subroutine zungqr (integer m, integer n, integer k, complex*16, dimension(
       lda, * ) a, integer lda, complex*16, dimension( * ) tau, complex*16,
       dimension( * ) work, integer lwork, integer info)
       ZUNGQR

💖 Purpose 💖

okay so ZUNGQR generates an M-by-N complex matrix Q with orthonormal columns, and it's defined as the first N columns of a product of K elementary reflectors of order M:

Q  =  H(1) H(2) . . . H(k)

as returned by ZGEQRF. slay ✨

💅 Parameters 💅

  • M — M is INTEGER and it's the number of rows of the matrix Q. Constraint: M >= 0. 🫶
  • N — N is INTEGER and it's the number of columns of the matrix Q. Constraint: M >= N >= 0. 🌸
  • K — K is INTEGER; it's the number of elementary reflectors whose product defines the matrix Q. Constraint: N >= K >= 0. 🎀
  • A — A is COMPLEX*16 array, dimension (LDA,N). On entry, the i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by ZGEQRF in the first k columns of its array argument A. On exit, the M-by-N matrix Q. ✨
  • LDA — LDA is INTEGER; it's the first dimension of the array A. Constraint: LDA >= max(1,M). 💜
  • TAU — TAU is COMPLEX*16 array, dimension (K). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by ZGEQRF. 🦋
  • WORK — WORK is COMPLEX*16 array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK. 🌈
  • LWORK — LWORK is INTEGER; it's the dimension of the array WORK. Constraint: LWORK >= max(1,N). For optimum performance LWORK >= N*NB, where NB is the optimal blocksize. 🍓 if you set 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 has an illegal value. 💀

🎀 Author 🎀

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

Definition at line 127 of file zungqr.f.

👑 Author 👑

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mwah 💋 that's the whole page, bestie. footer sign-off vibes: source SRC/zungqr.f(3) with LAPACK Version 3.12.0 — no separate date in the footer, so I'm not inventing one. 🎀✨

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