sorg2l(3S)

NAME
     SORG2L - generate an m by n real matrix Q with orthonormal columns,

SYNOPSIS
     SUBROUTINE SORG2L( M, N, K, A, LDA, TAU, WORK, INFO )

         INTEGER        INFO, K, LDA, M, N

         REAL           A( LDA, * ), 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
     SORG2L generates an m by n real matrix Q with orthonormal columns, which
     is defined as the last n columns of a product of k elementary reflectors
     of order m

           Q  =  H(k) . . . H(2) H(1)

     as returned by SGEQLF.


ARGUMENTS
     M       (input) INTEGER
             The number of rows of the matrix Q. M >= 0.

     N       (input) INTEGER
             The number of columns of the matrix Q. M >= N >= 0.

     K       (input) INTEGER
             The number of elementary reflectors whose product defines the
             matrix Q. N >= K >= 0.

     A       (input/output) REAL array, dimension (LDA,N)
             On entry, the (n-k+i)-th column must contain the vector which
             defines the elementary reflector H(i), for i = 1,2,...,k, as
             returned by SGEQLF in the last k columns of its array argument A.
             On exit, the m by n matrix Q.
     LDA     (input) INTEGER
             The first dimension of the array A. LDA >= max(1,M).

     TAU     (input) REAL array, dimension (K)
             TAU(i) must contain the scalar factor of the elementary reflector
             H(i), as returned by SGEQLF.

     WORK    (workspace) REAL array, dimension (N)

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

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

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