CUPGTR(3)

💖 NAME 💖

Hii bestie, welcome to cupgtr.f(3) — it's in the Library Functions Manual, and it's serving pure LAPACK subroutine energy. The file path on the page is /home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/cupgtr.f. That's the whole NAME section, no crumbs. 🫶

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

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

CUPGTR — yes, that's the subroutine, main character behavior only. 💅

🦋 Function/Subroutine Documentation 🦋

Here's the full signature, bestie:

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

And the label is literally CUPGTR. Iconic.

🌸 Purpose 🌸

CUPGTR 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 CHPTRD 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).

Like, it's literally assembling Q from the reflector besties that CHPTRD handed over. No cap. 💖

🎀 Parameters 🎀

• UPLO — UPLO is CHARACTER*1
  • = 'U': Upper triangular packed storage used in previous call to CHPTRD;
  • = 'L': Lower triangular packed storage used in previous call to CHPTRD.
• N — N is INTEGER
  • The order of the matrix Q. N >= 0.
• AP — AP is COMPLEX array, dimension (N*(N+1)/2)
  • The vectors which define the elementary reflectors, as returned by CHPTRD.
• TAU — TAU is COMPLEX array, dimension (N-1)
  • TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by CHPTRD.
• Q — Q is COMPLEX 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 array, dimension (N-1)
• INFO — INFO is INTEGER
  • = 0: successful exit
  • < 0: if INFO = -i, the i-th argument had an illegal value

bestie, if INFO < 0, an argument was illegal — not cute, but that's the rule. 😭

👑 Author 👑

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

Definition at line 113 of file cupgtr.f.

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

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Sign-off: this page is from LAPACK Version 3.12.0, path /home/abui...RC/cupgtr.f(3) — and the footer doesn't print a separate date, bestie, just that version/path combo. Slay. 💅✨