• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS
• FURTHER DETAILS

NAME

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

SYNOPSIS

  SUBROUTINE DLARZB( SIDE, TRANS, DIRECT, STOREV, M, N, K, L, V, LDV, 
 *      T, LDT, C, LDC, WORK, LDWORK)
  CHARACTER * 1 SIDE, TRANS, DIRECT, STOREV
  INTEGER M, N, K, L, LDV, LDT, LDC, LDWORK
  DOUBLE PRECISION V(LDV,*), T(LDT,*), C(LDC,*), WORK(LDWORK,*)

  SUBROUTINE DLARZB_64( SIDE, TRANS, DIRECT, STOREV, M, N, K, L, V, 
 *      LDV, T, LDT, C, LDC, WORK, LDWORK)
  CHARACTER * 1 SIDE, TRANS, DIRECT, STOREV
  INTEGER*8 M, N, K, L, LDV, LDT, LDC, LDWORK
  DOUBLE PRECISION V(LDV,*), T(LDT,*), C(LDC,*), WORK(LDWORK,*)

F95 INTERFACE

  SUBROUTINE LARZB( SIDE, TRANS, DIRECT, STOREV, [M], [N], K, L, V, 
 *       [LDV], T, [LDT], C, [LDC], [WORK], [LDWORK])
  CHARACTER(LEN=1) :: SIDE, TRANS, DIRECT, STOREV
  INTEGER :: M, N, K, L, LDV, LDT, LDC, LDWORK
  REAL(8), DIMENSION(:,:) :: V, T, C, WORK

  SUBROUTINE LARZB_64( SIDE, TRANS, DIRECT, STOREV, [M], [N], K, L, V, 
 *       [LDV], T, [LDT], C, [LDC], [WORK], [LDWORK])
  CHARACTER(LEN=1) :: SIDE, TRANS, DIRECT, STOREV
  INTEGER(8) :: M, N, K, L, LDV, LDT, LDC, LDWORK
  REAL(8), DIMENSION(:,:) :: V, T, C, WORK

C INTERFACE

#include <sunperf.h>

void dlarzb(char side, char trans, char direct, char storev, int m, int n, int k, int l, double *v, int ldv, double *t, int ldt, double *c, int ldc, int ldwork);

void dlarzb_64(char side, char trans, char direct, char storev, long m, long n, long k, long l, double *v, long ldv, double *t, long ldt, double *c, long ldc, long ldwork);

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)
  

   = 'L': apply H or H' from the Left

   = 'R': apply H or H' from the Right

• TRANS (input)
  

   = 'N': apply H (No transpose)

   = 'C': apply H' (Transpose)

• DIRECT (input)
  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)
  Indicates how the vectors which define the elementary reflectors are stored:

   = 'C': Columnwise                        (not supported yet)

   = 'R': Rowwise

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

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

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

• L (input)
  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)
  If STOREV = 'C', NV = K; if STOREV = 'R', NV = L.

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

• T (input)
  The triangular K-by-K matrix T in the representation of the block reflector.

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

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

• WORK (workspace)
  dimension(MAX(M,N),K)

• LDWORK (input)
  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