SRC/zupgtr.f(3)

📦
version 3.12.1 · 4 versions
, in arch rolling

🌸 NAME 🌸

SRC/zupgtr.f — that's the name, bestie, short and iconic 💅

✨ SYNOPSIS ✨

🌈 Functions/Subroutines 🌈

subroutine zupgtr (uplo, n, ap, tau, q, ldq, work, info)
           ZUPGTR

💖 Function/Subroutine Documentation 💖

🦋 subroutine zupgtr 🦋

subroutine zupgtr (character uplo, integer n, complex*16, dimension( * ) ap,
       complex*16, dimension( * ) tau, complex*16, dimension( ldq, * ) q,
       integer ldq, complex*16, dimension( * ) work, integer info)
       ZUPGTR

ZUPGTR is the main character here, no cap.

🎀 Purpose 🎀

Okay so ZUPGTR generates a complex unitary matrix Q which is defined as the product of n-1 elementary reflectors H(i) of order n, as returned by ZHPTRD using packed storage:

if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),

if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).

Literally the whole vibe: unpack those reflectors into Q 💖

🌟 Parameters 🌟

  • UPLO — UPLO is CHARACTER*1; = 'U': upper triangular packed storage used in previous call to ZHPTRD; = 'L': lower triangular packed storage used in previous call to ZHPTRD.
  • N — N is INTEGER; the order of the matrix Q. N >= 0.
  • AP — AP is COMPLEX*16 array, dimension (N*(N+1)/2); the vectors which define the elementary reflectors, as returned by ZHPTRD.
  • TAU — TAU is COMPLEX*16 array, dimension (N-1); TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by ZHPTRD.
  • Q — Q is COMPLEX*16 array, dimension (LDQ,N); the N-by-N unitary matrix Q.
  • LDQ — LDQ is INTEGER; the leading dimension of the array Q. LDQ >= max(1,N).
  • WORK — WORK is COMPLEX*16 array, dimension (N-1).
  • 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 113 of file zupgtr.f.

👑 Author 👑

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Sign-off tea 🫶 this page is from LAPACK Version 3.12.0, source SRC/zupgtr.f(3) — that's the footer moment, no extra date printed, just those details and good vibes ✨💜

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