SRC/ctrexc.f(3)

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version 3.12.1 · 7 versions
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🫶 SRC/ctrexc.f(3) 🫶

okay bestie, this page comes from the Library Functions Manual and it's giving major LAPACK energy. It's all about CTREXC, and yes, we're gonna keep every single detail because that's the vibe. 💅

💖 NAME 💖

SRC/ctrexc.f

✨ SYNOPSIS ✨

🧚 Functions/Subroutines 🧚

subroutine ctrexc (compq, n, t, ldt, q, ldq, ifst, ilst, info)

CTREXC

📚 Function/Subroutine Documentation 📚

subroutine ctrexc (character compq, integer n, complex, dimension( ldt, * )
       t, integer ldt, complex, dimension( ldq, * ) q, integer ldq, integer
       ifst, integer ilst, integer info)

CTREXC — main character behavior, fr fr.

🎀 Purpose 🎀

CTREXC reorders the Schur factorization of a complex matrix

A = Q*T*Q**H

so that the diagonal element of T with row index IFST is moved to row ILST.

The Schur form T is reordered by a unitary similarity transformation

Z**H*T*Z

and optionally the matrix Q of Schur vectors is updated by postmultiplying it with Z. That's the whole plot, no cap. 🦋

🌈 Parameters 🌈

💖 COMPQ 💖

COMPQ is CHARACTER*1

  • = 'V': update the matrix Q of Schur vectors;
  • = 'N': do not update Q.

🍓 N 🍓

N is INTEGER

The order of the matrix T. N >= 0.

If N == 0 arguments ILST and IFST may be any value.

🔥 T 🔥

T is COMPLEX array, dimension (LDT,N)

On entry, the upper triangular matrix T.

On exit, the reordered upper triangular matrix.

👑 LDT 👑

LDT is INTEGER

The leading dimension of the array T. LDT >= max(1,N).

🌸 Q 🌸

Q is COMPLEX array, dimension (LDQ,N)

On entry, if COMPQ = 'V', the matrix Q of Schur vectors.

On exit, if COMPQ = 'V', Q has been postmultiplied by the unitary transformation matrix Z which reorders T.

If COMPQ = 'N', Q is not referenced.

🧚 LDQ 🧚

LDQ is INTEGER

The leading dimension of the array Q. LDQ >= 1, and if COMPQ = 'V', LDQ >= max(1,N).

💜 IFST 💜

IFST is INTEGER

That's the whole note for IFST, bestie. No extra lore here.

🦋 ILST 🦋

ILST is INTEGER

Specify the reordering of the diagonal elements of T:

The element with row index IFST is moved to row ILST by a sequence of transpositions between adjacent elements.

1 <= IFST <= N; 1 <= ILST <= N.

⭐ 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 ctrexc.f.

🧚 Author 🧚

Generated automatically by Doxygen for LAPACK from the source code.

okay that's the whole page, bestie. Footer sign-off, as requested: LAPACK, Version 3.12.0, page SRC/ctrexc.f(3) — kisses from the Library Functions Manual 🫶💅🎀

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