SRC/dopgtr.f(3)

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version 3.12.1 · 7 versions
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💅 NAME

Okay so bestie, this page is SRC/dopgtr.f(3) from the Library Functions Manual, and the name on the tin is literally SRC/dopgtr.f. Slay.

🌸 SYNOPSIS

Functions/Subroutines

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

🦋 Function/Subroutine Documentation

Here’s the full signature, no cap:

subroutine dopgtr (character uplo, integer n, double precision, dimension( * ) ap, double precision, dimension( * ) tau, double precision, dimension( ldq, * ) q, integer ldq, double precision, dimension( * ) work, integer info)

DOPGTR

🎯 Purpose

DOPGTR generates a real orthogonal matrix Q which is defined as the product of n-1 elementary reflectors H(i) of order n, as returned by DSPTRD 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).

🍓 Parameters

UPLO

UPLO is CHARACTER*1

  • = 'U': Upper triangular packed storage used in previous call to DSPTRD;
  • = 'L': Lower triangular packed storage used in previous call to DSPTRD.

N

N is INTEGER

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

AP

AP is DOUBLE PRECISION array, dimension (N*(N+1)/2)

The vectors which define the elementary reflectors, as returned by DSPTRD.

TAU

TAU is DOUBLE PRECISION array, dimension (N-1)

TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DSPTRD.

Q

Q is DOUBLE PRECISION array, dimension (LDQ,N)

The N-by-N orthogonal matrix Q.

LDQ

LDQ is INTEGER

The leading dimension of the array Q. LDQ >= max(1,N).

WORK

WORK is DOUBLE PRECISION 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 dopgtr.f.

🧚 Author

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