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# cunmtr

```
NAME
CUNMTR - overwrite the general complex M-by-N matrix C with
SIDE = 'L' SIDE = 'R' TRANS = 'N'

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

CHARACTER      SIDE, TRANS, UPLO

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

COMPLEX        A( LDA, * ), C( LDC, * ), TAU( * ), WORK(
LWORK )

PURPOSE
CUNMTR overwrites the general complex M-by-N matrix C with
TRANS = 'C':      Q**H * C       C * Q**H

where Q is a complex unitary 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
CHETRD:

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**H from the Left;
= 'R': apply Q or Q**H from the Right.

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

TRANS   (input) CHARACTER*1
= 'N':  No transpose, apply Q;
= 'C':  Conjugate transpose, apply Q**H.

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) COMPLEX array, dimension
(LDA,M) if SIDE = 'L' (LDA,N) if SIDE = 'R' The vec-
tors which define the elementary reflectors, as

returned by CHETRD.

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) COMPLEX array, dimension
(M-1) if SIDE = 'L' (N-1) if SIDE = 'R' TAU(i) must
contain the scalar factor of the elementary reflec-
tor H(i), as returned by CHETRD.

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

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

WORK    (workspace) COMPLEX 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.

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