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).

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

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

November 2011