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PDORMBR(l)			       )			    PDORMBR(l)

NAME
       PDORMBR	-  VECT	= 'Q', PDORMBR overwrites the general real distributed
       M-by-N matrix sub( C ) =	C(IC:IC+M-1,JC:JC+N-1) with  SIDE = 'L'	SIDE =
       'R' TRANS = 'N'

SYNOPSIS
       SUBROUTINE PDORMBR( VECT,  SIDE,	TRANS, M, N, K,	A, IA, JA, DESCA, TAU,
			   C, IC, JC, DESCC, WORK, LWORK, INFO )

	   CHARACTER	   SIDE, TRANS,	VECT

	   INTEGER	   IA, IC, INFO, JA, JC, K, LWORK, M, N

	   INTEGER	   DESCA( * ), DESCC( *	)

	   DOUBLE	   PRECISION A(	* ), C(	* ), TAU( * ), WORK( * )

PURPOSE
       If VECT = 'Q', PDORMBR overwrites the general real  distributed	M-by-N
       matrix  sub(  C	)  = C(IC:IC+M-1,JC:JC+N-1) with SIDE =	'L' SIDE = 'R'
       TRANS = 'N': Q *	sub( C ) sub( C	) * Q TRANS = 'T':	Q**T * sub(  C
       )       sub( C )	* Q**T

       If VECT = 'P', PDORMBR overwrites sub( C	) with

			    SIDE = 'L'		 SIDE =	'R'
       TRANS = 'N':	 P * sub( C )	       sub( C )	* P
       TRANS = 'T':	 P**T *	sub( C )       sub( C )	* P**T

       Here  Q	and P**T are the orthogonal distributed	matrices determined by
       PDGEBRD when reducing a real distributed	matrix A(IA:*,JA:*) to bidiag-
       onal form: A(IA:*,JA:*) = Q * B * P**T. Q and P**T are defined as prod-
       ucts of elementary reflectors H(i) and G(i) respectively.

       Let nq =	m if SIDE = 'L'	and nq = n if SIDE = 'R'. Thus nq is the order
       of the orthogonal matrix	Q or P**T that is applied.

       If VECT = 'Q', A(IA:*,JA:*) is assumed to have been an NQ-by-K matrix:
       if nq >=	k, Q = H(1) H(2) . . . H(k);
       if nq < k, Q = H(1) H(2)	. . . H(nq-1).

       If VECT = 'P', A(IA:*,JA:*) is assumed to have been a K-by-NQ matrix:
       if k < nq, P = G(1) G(2)	. . . G(k);
       if k >= nq, P = G(1) G(2) . . . G(nq-1).

       Notes
       =====

       Each  global data object	is described by	an associated description vec-
       tor.  This vector stores	the information	required to establish the map-
       ping between an object element and its corresponding process and	memory
       location.

       Let A be	a generic term for any 2D block	 cyclicly  distributed	array.
       Such a global array has an associated description vector	DESCA.	In the
       following comments, the character _ should be read as  "of  the	global
       array".

       NOTATION	       STORED IN      EXPLANATION
       ---------------	--------------	--------------------------------------
       DTYPE_A(global) DESCA( DTYPE_ )The descriptor type.  In this case,
				      DTYPE_A =	1.
       CTXT_A (global) DESCA( CTXT_ ) The BLACS	context	handle,	indicating
				      the BLACS	process	grid A is distribu-
				      ted over.	The context itself is glo-
				      bal, but the handle (the integer
				      value) may vary.
       M_A    (global) DESCA( M_ )    The number of rows in the	global
				      array A.
       N_A    (global) DESCA( N_ )    The number of columns in the global
				      array A.
       MB_A   (global) DESCA( MB_ )   The blocking factor used to distribute
				      the rows of the array.
       NB_A   (global) DESCA( NB_ )   The blocking factor used to distribute
				      the columns of the array.
       RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
				      row  of  the  array  A  is  distributed.
       CSRC_A (global) DESCA( CSRC_ ) The process column over which the
				      first column of the array	A is
				      distributed.
       LLD_A  (local)  DESCA( LLD_ )  The leading dimension of the local
				      array.  LLD_A >= MAX(1,LOCr(M_A)).

       Let K be	the number of rows or columns of a distributed matrix, and as-
       sume that its process grid has dimension	p x q.
       LOCr( K ) denotes the number of elements	of K that a process would  re-
       ceive if	K were distributed over	the p processes	of its process column.
       Similarly, LOCc(	K ) denotes the	number of elements of K	that a process
       would receive if	K were distributed over	the q processes	of its process
       row.
       The  values  of	LOCr()	and LOCc() may be determined via a call	to the
       ScaLAPACK tool function,	NUMROC:
	       LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
	       LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).  An	 upper
       bound for these quantities may be computed by:
	       LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
	       LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A

ARGUMENTS
       VECT    (global input) CHARACTER
	       = 'Q': apply Q or Q**T;
	       = 'P': apply P or P**T.

       SIDE    (global input) CHARACTER
	       = 'L': apply Q, Q**T, P or P**T from the	Left;
	       = 'R': apply Q, Q**T, P or P**T from the	Right.

       TRANS   (global input) CHARACTER
	       = 'N':  No transpose, apply Q or	P;
	       = 'T':  Transpose, apply	Q**T or	P**T.

       M       (global input) INTEGER
	       The  number of rows to be operated on i.e the number of rows of
	       the distributed submatrix sub( C	). M >=	0.

       N       (global input) INTEGER
	       The number of columns to	be operated on i.e the number of  col-
	       umns of the distributed submatrix sub( C	). N >=	0.

       K       (global input) INTEGER
	       If  VECT	 = 'Q',	the number of columns in the original distrib-
	       uted matrix reduced by PDGEBRD.	If VECT	= 'P', the  number  of
	       rows  in	the original distributed matrix	reduced	by PDGEBRD.  K
	       >= 0.

       A       (local input) DOUBLE PRECISION pointer into the local memory
	       to  an  array  of  dimension  (LLD_A,LOCc(JA+MIN(NQ,K)-1))   if
	       VECT='Q',  and  (LLD_A,LOCc(JA+NQ-1))  if VECT =	'P'. NQ	= M if
	       SIDE = 'L', and NQ = N otherwise. The vectors which define  the
	       elementary  reflectors  H(i) and	G(i), whose products determine
	       the matrices Q and P, as	returned by PDGEBRD.  If VECT  =  'Q',
	       LLD_A   >=  max(1,LOCr(IA+NQ-1));  if  VECT  =  'P',  LLD_A  >=
	       max(1,LOCr(IA+MIN(NQ,K)-1)).

       IA      (global input) INTEGER
	       The row index in	the global array A indicating the first	row of
	       sub( A ).

       JA      (global input) INTEGER
	       The  column  index  in  the global array	A indicating the first
	       column of sub( A	).

       DESCA   (global and local input)	INTEGER	array of dimension DLEN_.
	       The array descriptor for	the distributed	matrix A.

       TAU     (local input) DOUBLE PRECISION array, dimension
	       LOCc(JA+MIN(NQ,K)-1) if VECT  =	'Q',  LOCr(IA+MIN(NQ,K)-1)  if
	       VECT  =	'P', TAU(i) must contain the scalar factor of the ele-
	       mentary	reflector H(i) or G(i),	which determines Q  or	P,  as
	       returned	by PDGEBRD in its array	argument TAUQ or TAUP.	TAU is
	       tied to the distributed matrix A.

       C       (local input/local output) DOUBLE PRECISION pointer into	the
	       local memory to an array	of dimension (LLD_C,LOCc(JC+N-1)).  On
	       entry,  the  local pieces of the	distributed matrix sub(C).  On
	       exit, if	VECT='Q', sub( C ) is overwritten by  Q*sub(  C	 )  or
	       Q'*sub(	C ) or sub( C )*Q' or sub( C )*Q; if VECT='P, sub( C )
	       is overwritten by P*sub(	C ) or P'*sub( C ) or sub(  C  )*P  or
	       sub( C )*P'.

       IC      (global input) INTEGER
	       The row index in	the global array C indicating the first	row of
	       sub( C ).

       JC      (global input) INTEGER
	       The column index	in the global array  C	indicating  the	 first
	       column of sub( C	).

       DESCC   (global and local input)	INTEGER	array of dimension DLEN_.
	       The array descriptor for	the distributed	matrix C.

       WORK    (local workspace/local output) DOUBLE PRECISION array,
	       dimension  (LWORK) On exit, WORK(1) returns the minimal and op-
	       timal LWORK.

       LWORK   (local or global	input) INTEGER
	       The dimension of	the array WORK.	 LWORK is local	input and must
	       be at least If SIDE = 'L', NQ = M; if( (VECT = 'Q' and NQ >= K)
	       or (VECT	<> 'Q' and NQ >	K)  ),	IAA=IA;	 JAA=JA;  MI=M;	 NI=N;
	       ICC=IC;	JCC=JC;	else IAA=IA+1; JAA=JA; MI=M-1; NI=N; ICC=IC+1;
	       JCC=JC; end if else if SIDE = 'R', NQ = N; if( (VECT = 'Q'  and
	       NQ  >=  K) or (VECT <> 'Q' and NQ > K) ), IAA=IA; JAA=JA; MI=M;
	       NI=N; ICC=IC; JCC=JC;  else  IAA=IA;  JAA=JA+1;	MI=M;  NI=N-1;
	       ICC=IC; JCC=JC+1; end if	end if

	       If  VECT	= 'Q', If SIDE = 'L', LWORK >= MAX( (NB_A*(NB_A-1))/2,
	       (NqC0 + MpC0)*NB_A ) + NB_A * NB_A else if SIDE = 'R', LWORK >=
	       MAX(  (NB_A*(NB_A-1))/2,	 (  NqC0 + MAX(	NpA0 + NUMROC( NUMROC(
	       NI+ICOFFC, NB_A,	0, 0, NPCOL ), NB_A, 0,	 0,  LCMQ  ),  MpC0  )
	       )*NB_A  )  +  NB_A * NB_A end if	else if	VECT <>	'Q', if	SIDE =
	       'L', LWORK >= MAX( (MB_A*(MB_A-1))/2, ( MpC0 + MAX( MqA0	+ NUM-
	       ROC(  NUMROC(  MI+IROFFC, MB_A, 0, 0, NPROW ), MB_A, 0, 0, LCMP
	       ), NqC0 ) )*MB_A	) + MB_A * MB_A	else if	SIDE = 'R',  LWORK  >=
	       MAX(  (MB_A*(MB_A-1))/2,	(MpC0 +	NqC0)*MB_A ) + MB_A * MB_A end
	       if end if

	       where LCMP = LCM	/ NPROW, LCMQ =	LCM / NPCOL, with LCM =	 ICLM(
	       NPROW, NPCOL ),

	       IROFFA =	MOD( IAA-1, MB_A ), ICOFFA = MOD( JAA-1, NB_A ), IAROW
	       = INDXG2P( IAA, MB_A, MYROW, RSRC_A, NPROW ), IACOL =  INDXG2P(
	       JAA,  NB_A,  MYCOL,  CSRC_A, NPCOL ), MqA0 = NUMROC( MI+ICOFFA,
	       NB_A, MYCOL, IACOL, NPCOL ), NpA0 =  NUMROC(  NI+IROFFA,	 MB_A,
	       MYROW, IAROW, NPROW ),

	       IROFFC =	MOD( ICC-1, MB_C ), ICOFFC = MOD( JCC-1, NB_C ), ICROW
	       = INDXG2P( ICC, MB_C, MYROW, RSRC_C, NPROW ), ICCOL =  INDXG2P(
	       JCC,  NB_C,  MYCOL,  CSRC_C, NPCOL ), MpC0 = NUMROC( MI+IROFFC,
	       MB_C, MYROW, ICROW, NPROW ), NqC0 =  NUMROC(  NI+ICOFFC,	 NB_C,
	       MYCOL, ICCOL, NPCOL ),

	       INDXG2P	and NUMROC are ScaLAPACK tool functions; MYROW,	MYCOL,
	       NPROW and NPCOL can be determined  by  calling  the  subroutine
	       BLACS_GRIDINFO.

	       If LWORK	= -1, then LWORK is global input and a workspace query
	       is assumed; the routine only calculates the minimum and optimal
	       size  for  all work arrays. Each	of these values	is returned in
	       the first entry of the corresponding work array,	and  no	 error
	       message is issued by PXERBLA.

       INFO    (global output) INTEGER
	       = 0:  successful	exit
	       <  0:   If the i-th argument is an array	and the	j-entry	had an
	       illegal value, then INFO	= -(i*100+j), if the i-th argument  is
	       a scalar	and had	an illegal value, then INFO = -i.

	       Alignment requirements ======================

	       The     distributed     submatrices     A(IA:*,	  JA:*)	   and
	       C(IC:IC+M-1,JC:JC+N-1) must verify some	alignment  properties,
	       namely the following expressions	should be true:

	       If   VECT   =   'Q',  If	 SIDE  =  'L',	(  MB_A.EQ.MB_C	 .AND.
	       IROFFA.EQ.IROFFC	.AND.  IAROW.EQ.ICROW  )  If  SIDE  =  'R',  (
	       MB_A.EQ.NB_C  .AND.  IROFFA.EQ.ICOFFC  )	 else If SIDE =	'L', (
	       MB_A.EQ.MB_C  .AND.  ICOFFA.EQ.IROFFC  )	 If  SIDE  =  'R',   (
	       NB_A.EQ.NB_C  .AND. ICOFFA.EQ.ICOFFC .AND. IACOL.EQ.ICCOL ) end
	       if

ScaLAPACK version 1.7		13 August 2001			    PDORMBR(l)

NAME | SYNOPSIS | PURPOSE | ARGUMENTS

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