• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

dopgtr - generate a real orthogonal matrix Q which is defined as the product of n-1 elementary reflectors H(i) of order n, as returned by SSPTRD using packed storage

SYNOPSIS

  SUBROUTINE DOPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO)
  CHARACTER * 1 UPLO
  INTEGER N, LDQ, INFO
  DOUBLE PRECISION AP(*), TAU(*), Q(LDQ,*), WORK(*)

  SUBROUTINE DOPGTR_64( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO)
  CHARACTER * 1 UPLO
  INTEGER*8 N, LDQ, INFO
  DOUBLE PRECISION AP(*), TAU(*), Q(LDQ,*), WORK(*)

F95 INTERFACE

  SUBROUTINE OPGTR( UPLO, [N], AP, TAU, Q, [LDQ], [WORK], [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER :: N, LDQ, INFO
  REAL(8), DIMENSION(:) :: AP, TAU, WORK
  REAL(8), DIMENSION(:,:) :: Q

  SUBROUTINE OPGTR_64( UPLO, [N], AP, TAU, Q, [LDQ], [WORK], [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER(8) :: N, LDQ, INFO
  REAL(8), DIMENSION(:) :: AP, TAU, WORK
  REAL(8), DIMENSION(:,:) :: Q

C INTERFACE

#include <sunperf.h>

void dopgtr(char uplo, int n, double *ap, double *tau, double *q, int ldq, int *info);

void dopgtr_64(char uplo, long n, double *ap, double *tau, double *q, long ldq, long *info);

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 SSPTRD 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).

ARGUMENTS

• UPLO (input)
  

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

• N (input)
  The order of the matrix Q. N > = 0.

• AP (input)
  The vectors which define the elementary reflectors, as returned by SSPTRD.

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

• Q (output)
  The N-by-N orthogonal matrix Q.

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

• WORK (workspace)
  dimension(N-1)

• INFO (output)
  

   = 0:  successful exit

   < 0:  if INFO  = -i, the i-th argument had an illegal value