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

NAME

dorghr - generate a real orthogonal matrix Q which is defined as the product of IHI-ILO elementary reflectors of order N, as returned by SGEHRD

SYNOPSIS

  SUBROUTINE DORGHR( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
  INTEGER N, ILO, IHI, LDA, LWORK, INFO
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)

  SUBROUTINE DORGHR_64( N, ILO, IHI, A, LDA, TAU, WORK, LWORK, INFO)
  INTEGER*8 N, ILO, IHI, LDA, LWORK, INFO
  DOUBLE PRECISION A(LDA,*), TAU(*), WORK(*)

F95 INTERFACE

  SUBROUTINE ORGHR( [N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK], 
 *       [INFO])
  INTEGER :: N, ILO, IHI, LDA, LWORK, INFO
  REAL(8), DIMENSION(:) :: TAU, WORK
  REAL(8), DIMENSION(:,:) :: A

  SUBROUTINE ORGHR_64( [N], ILO, IHI, A, [LDA], TAU, [WORK], [LWORK], 
 *       [INFO])
  INTEGER(8) :: N, ILO, IHI, LDA, LWORK, INFO
  REAL(8), DIMENSION(:) :: TAU, WORK
  REAL(8), DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void dorghr(int n, int ilo, int ihi, double *a, int lda, double *tau, int *info);

void dorghr_64(long n, long ilo, long ihi, double *a, long lda, double *tau, long *info);

PURPOSE

dorghr generates a real orthogonal matrix Q which is defined as the product of IHI-ILO elementary reflectors of order N, as returned by SGEHRD:

Q = H(ilo) H(ilo+1) . . . H(ihi-1).

ARGUMENTS

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

• ILO (input)
  ILO and IHI must have the same values as in the previous call of SGEHRD. Q is equal to the unit matrix except in the submatrix Q(ilo+1:ihi,ilo+1:ihi). 1 < = ILO < = IHI < = N, if N > 0; ILO =1 and IHI =0, if N =0.

• IHI (input)
  See the description of ILO.

• A (input/output)
  On entry, the vectors which define the elementary reflectors, as returned by SGEHRD. On exit, the N-by-N orthogonal matrix Q.

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

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

• WORK (workspace)
  On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

• LWORK (input)
  The dimension of the array WORK. LWORK > = IHI-ILO. For optimum performance LWORK > = (IHI-ILO)*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 (output)
  

   = 0:  successful exit

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