SRC/sorgtr.f(3)

💖 NAME 💖

okay so this page is SRC/sorgtr.f, and we’re in the Library Functions Manual — folding that manual-name vibe in right here so you know exactly where you are, bestie. It’s all about the sorgtr life. 💅

---

🦋 SYNOPSIS 🦋

✨ Functions/Subroutines ✨

• subroutine sorgtr (uplo, n, a, lda, tau, work, lwork, info) — the one and only SORGTR, living its short-signature life.

---

🌸 Function/Subroutine Documentation 🌸

subroutine sorgtr (character uplo, integer n, real, dimension( lda, * ) a,
       integer lda, real, dimension( * ) tau, real, dimension( * ) work,
       integer lwork, integer info)

SORGTR — yes, that’s the icon we’re documenting. 💅

✨ Purpose ✨

okay so the glow-up: SORGTR generates a real orthogonal matrix Q which is defined as the product of n-1 elementary reflectors of order N, as returned by SSYTRD:

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

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

🎀 Parameters 🎀

• UPLO — UPLO is CHARACTER*1. It’s giving directions:
  • = 'U': Upper triangle of A contains elementary reflectors from SSYTRD;
  • = 'L': Lower triangle of A contains elementary reflectors from SSYTRD.
• N — N is INTEGER. It’s the order of the matrix Q. N >= 0.
• A — A is REAL array, dimension (LDA,N). On entry, it’s the vectors which define the elementary reflectors, as returned by SSYTRD. On exit, it’s the N-by-N orthogonal matrix Q. main character transformation, honestly.
• LDA — LDA is INTEGER. It’s the leading dimension of the array A. LDA >= max(1,N).
• TAU — TAU is REAL array, dimension (N-1). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SSYTRD.
• WORK — WORK is REAL 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. LWORK >= max(1,N-1). For optimum performance LWORK >= (N-1)*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. Exit-status tea:
  • = 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 122 of file sorgtr.f.

---

🌈 Author 🌈

Generated automatically by Doxygen for LAPACK from the source code.

---

Catch you later, bestie 💅✨ — source/version footer check: LAPACK, Version 3.12.0, and this page is SRC/sorgtr.f(3). The footer doesn’t list a separate date, just the version and file-page moment. 🫶