# dopgtr.f man page

dopgtr.f

## Synopsis

### Functions/Subroutines

subroutine **dopgtr** (UPLO, **N**, AP, TAU, Q, LDQ, WORK, INFO)**DOPGTR**

## Function/Subroutine Documentation

### 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.

**Date:**December 2016

Definition at line 116 of file dopgtr.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dopgtr(3) is an alias of dopgtr.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK