dlarzb(3S)

NAME
     DLARZB - applie a real block reflector H or its transpose H**T to a real
     distributed M-by-N C from the left or the right

SYNOPSIS
     SUBROUTINE DLARZB( SIDE, TRANS, DIRECT, STOREV, M, N, K, L, V, LDV, T,
                        LDT, C, LDC, WORK, LDWORK )

         CHARACTER      DIRECT, SIDE, STOREV, TRANS

         INTEGER        K, L, LDC, LDT, LDV, LDWORK, M, N

         DOUBLE         PRECISION C( LDC, * ), T( LDT, * ), V( LDV, * ), WORK(
                        LDWORK, * )

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
     DLARZB applies a real block reflector H or its transpose H**T to a real
     distributed M-by-N C from the left or the right. Currently, only STOREV =
     'R' and DIRECT = 'B' are supported.


ARGUMENTS
     SIDE    (input) CHARACTER*1
             = 'L': apply H or H' from the Left
             = 'R': apply H or H' from the Right

     TRANS   (input) CHARACTER*1
             = 'N': apply H (No transpose)
             = 'C': apply H' (Transpose)

     DIRECT  (input) CHARACTER*1
             Indicates how H is formed from a product of elementary reflectors
             = 'F': H = H(1) H(2) . . . H(k) (Forward, not supported yet)
             = 'B': H = H(k) . . . H(2) H(1) (Backward)

     STOREV  (input) CHARACTER*1
             Indicates how the vectors which define the elementary reflectors
             are stored:
             = 'C': Columnwise                        (not supported yet)
             = 'R': Rowwise

     M       (input) INTEGER
             The number of rows of the matrix C.

     N       (input) INTEGER
             The number of columns of the matrix C.

     K       (input) INTEGER
             The order of the matrix T (= the number of elementary reflectors
             whose product defines the block reflector).

     L       (input) INTEGER
             The number of columns of the matrix V containing the meaningful
             part of the Householder reflectors.  If SIDE = 'L', M >= L >= 0,
             if SIDE = 'R', N >= L >= 0.

     V       (input) DOUBLE PRECISION array, dimension (LDV,NV).
             If STOREV = 'C', NV = K; if STOREV = 'R', NV = L.

     LDV     (input) INTEGER
             The leading dimension of the array V.  If STOREV = 'C', LDV >= L;
             if STOREV = 'R', LDV >= K.

     T       (input) DOUBLE PRECISION array, dimension (LDT,K)
             The triangular K-by-K matrix T in the representation of the block
             reflector.

     LDT     (input) INTEGER
             The leading dimension of the array T. LDT >= K.

     C       (input/output) DOUBLE PRECISION array, dimension (LDC,N)
             On entry, the M-by-N matrix C.  On exit, C is overwritten by H*C
             or H'*C or C*H or C*H'.

     LDC     (input) INTEGER
             The leading dimension of the array C. LDC >= max(1,M).

     WORK    (workspace) DOUBLE PRECISION array, dimension (LDWORK,K)

     LDWORK  (input) INTEGER
             The leading dimension of the array WORK.  If SIDE = 'L', LDWORK
             >= max(1,N); if SIDE = 'R', LDWORK >= max(1,M).

FURTHER DETAILS
     Based on contributions by
       A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA

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

     This man page is available only online.