sopgtr(3S)

NAME
     SOPGTR - 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 SOPGTR( UPLO, N, AP, TAU, Q, LDQ, WORK, INFO )

         CHARACTER      UPLO

         INTEGER        INFO, LDQ, N

         REAL           AP( * ), Q( LDQ, * ), TAU( * ), WORK( * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

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

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

     TAU     (input) REAL array, dimension (N-1)
             TAU(i) must contain the scalar factor of the elementary reflector
             H(i), as returned by SSPTRD.
     Q       (output) REAL array, dimension (LDQ,N)
             The N-by-N orthogonal matrix Q.

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

     WORK    (workspace) REAL array, dimension (N-1)

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

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

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