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RedHat 9 (Linux i386) - man page for dormtr (redhat section l)

DORMTR(l)					)					DORMTR(l)

NAME
       DORMTR  -  overwrite  the general real M-by-N matrix C with  SIDE = 'L' SIDE = 'R' TRANS =
       'N'

SYNOPSIS
       SUBROUTINE DORMTR( SIDE, UPLO, TRANS, M, N, A, LDA, TAU, C, LDC, WORK, LWORK, INFO )

	   CHARACTER	  SIDE, TRANS, UPLO

	   INTEGER	  INFO, LDA, LDC, LWORK, M, N

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

PURPOSE
       DORMTR overwrites the general real M-by-N matrix C with SIDE = 'L' SIDE = 'R' TRANS = 'N':
       Q * C C * Q TRANS = 'T':      Q**T * C	    C * Q**T

       where  Q  is a real orthogonal matrix of order nq, with nq = m if SIDE = 'L' and nq = n if
       SIDE = 'R'. Q is defined as the product of nq-1	elementary  reflectors,  as  returned  by
       DSYTRD:

       if UPLO = 'U', Q = H(nq-1) . . . H(2) H(1);

       if UPLO = 'L', Q = H(1) H(2) . . . H(nq-1).

ARGUMENTS
       SIDE    (input) CHARACTER*1
	       = 'L': apply Q or Q**T from the Left;
	       = 'R': apply Q or Q**T from the Right.

       UPLO    (input) CHARACTER*1
	       =  'U':	Upper  triangle  of  A contains elementary reflectors from DSYTRD; = 'L':
	       Lower triangle of A contains elementary reflectors from DSYTRD.

       TRANS   (input) CHARACTER*1
	       = 'N':  No transpose, apply Q;
	       = 'T':  Transpose, apply Q**T.

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

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

       A       (input) DOUBLE PRECISION array, dimension
	       (LDA,M) if SIDE = 'L' (LDA,N) if SIDE = 'R' The vectors which define  the  elemen-
	       tary reflectors, as returned by DSYTRD.

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

       TAU     (input) DOUBLE PRECISION array, dimension
	       (M-1) if SIDE = 'L' (N-1) if SIDE = 'R' TAU(i) must contain the scalar  factor  of
	       the elementary reflector H(i), as returned by DSYTRD.

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

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

       WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
	       On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

       LWORK   (input) INTEGER
	       The dimension of the array WORK.  If SIDE = 'L', LWORK >= max(1,N); if SIDE = 'R',
	       LWORK >= max(1,M).  For optimum performance LWORK >= N*NB if SIDE = 'L', and LWORK
	       >= M*NB if SIDE = 'R', where NB is the optimal blocksize.

	       If LWORK = -1, then a workspace query is assumed; the routine only calculates  the
	       optimal	size of the WORK array, returns this value as the first entry of the WORK
	       array, and no error message related to LWORK is issued by XERBLA.

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

LAPACK version 3.0			   15 June 2000 				DORMTR(l)


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