SRC/dorgtr.f(3)

🌸 NAME 🌸

SRC/dorgtr.f — okay bestie, this is the page for SRC/dorgtr.f, straight out of the Library Functions Manual. It’s the DORGTR subroutine from LAPACK and it’s lowkey iconic 💅

---

💅 SYNOPSIS 💅

✨ Functions/Subroutines ✨

subroutine dorgtr (uplo, n, a, lda, tau, work, lwork, info)
    DORGTR

---

🦋 Function/Subroutine Documentation 🦋

The whole signature situation is literally:

subroutine dorgtr (character uplo, integer n, double precision, dimension(
     lda, * ) a, integer lda, double precision, dimension( * ) tau, double
     precision, dimension( * ) work, integer lwork, integer info)
    DORGTR

✨ Purpose ✨

DORGTR generates a real orthogonal matrix Q which is defined as the product of n-1 elementary reflectors of order N, as returned by DSYTRD:

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

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

No cap, that’s the whole vibe of what it does 🫶

🎀 Parameters 🎀

• UPLO — CHARACTER*1.
  • = 'U': Upper triangle of A contains elementary reflectors from DSYTRD;
  • = 'L': Lower triangle of A contains elementary reflectors from DSYTRD.
• N — INTEGER. The order of the matrix Q. N >= 0.
• A — DOUBLE PRECISION array, dimension (LDA,N). On entry, the vectors which define the elementary reflectors, as returned by DSYTRD. On exit, the N-by-N orthogonal matrix Q.
• LDA — INTEGER. The leading dimension of the array A. LDA >= max(1,N).
• TAU — DOUBLE PRECISION array, dimension (N-1). TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DSYTRD.
• WORK — DOUBLE PRECISION array, dimension (MAX(1,LWORK)). On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
• LWORK — INTEGER. 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 — 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 122 of file dorgtr.f.

---

💫 Author 💫

Generated automatically by Doxygen for LAPACK from the source code.

---

bestie, this cutie was rendered by LAPACK Version 3.12.0, source file SRC/dorgtr.f(3) 💖✨🎀