SOPGTR(3)      LAPACK routine of NEC Numeric Library Collection      SOPGTR(3)



NAME
       SOPGTR

SYNOPSIS
       SUBROUTINE SOPGTR (UPLO, N, AP, TAU, Q, LDQ, WORK, INFO)



PURPOSE
            SOPGTR 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)
                     UPLO is CHARACTER*1
                     = 'U': Upper triangular packed storage used in previous
                            call to SSPTRD;
                     = 'L': Lower triangular packed storage used in previous
                            call to SSPTRD.

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

           AP        (input)
                     AP is REAL array, dimension (N*(N+1)/2)
                     The vectors which define the elementary reflectors, as
                     returned by SSPTRD.

           TAU       (input)
                     TAU is REAL array, dimension (N-1)
                     TAU(i) must contain the scalar factor of the elementary
                     reflector H(i), as returned by SSPTRD.

           Q         (output)
                     Q is REAL array, dimension (LDQ,N)
                     The N-by-N orthogonal matrix Q.

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

           WORK      (output)
                     WORK is REAL array, dimension (N-1)

           INFO      (output)
                     INFO is INTEGER
                     = 0:  successful exit
                     < 0:  if INFO = -i, the i-th argument had an illegal value



LAPACK routine                  31 October 2017                      SOPGTR(3)