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).

SIDE

          SIDE is CHARACTER*1


          = 'L': apply Q or Q**T from the Left;


          = 'R': apply Q or Q**T from the Right.

UPLO

          UPLO is CHARACTER*1


          = 'U': Upper triangle of A contains elementary reflectors


                 from DSYTRD;


          = 'L': Lower triangle of A contains elementary reflectors


                 from DSYTRD.

TRANS

          TRANS is CHARACTER*1


          = 'N':  No transpose, apply Q;


          = 'T':  Transpose, apply Q**T.

M

          M is INTEGER


          The number of rows of the matrix C. M >= 0.

N

          N is INTEGER


          The number of columns of the matrix C. N >= 0.

A

          A is DOUBLE PRECISION array, dimension


                               (LDA,M) if SIDE = 'L'


                               (LDA,N) if SIDE = 'R'


          The vectors which define the elementary reflectors, as


          returned by DSYTRD.

LDA

          LDA is INTEGER


          The leading dimension of the array A.


          LDA >= max(1,M) if SIDE = 'L'; LDA >= max(1,N) if SIDE = 'R'.

TAU

          TAU is 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

          C is 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

          LDC is INTEGER


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

WORK

          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))


          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

LWORK

          LWORK is 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

          INFO is INTEGER


          = 0:  successful exit


          < 0:  if INFO = -i, the i-th argument had an illegal value

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NAG Ltd.

December 2016