cunmtr.f −

**Functions/Subroutines**

subroutine **cunmtr** (SIDE, UPLO, TRANS, M, N, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)

CUNMTR

**subroutine cunmtr (characterSIDE, characterUPLO, characterTRANS, integerM, integerN, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( ldc, * )C, integerLDC, complex, dimension( * )WORK, integerLWORK, integerINFO)
CUNMTR**

**Purpose:**

CUNMTR overwrites the general complex M-by-N matrix C with

SIDE = ’L’ SIDE = ’R’

TRANS = ’N’: Q * C C * Q

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).

**Parameters:**

*SIDE*

SIDE is CHARACTER*1

= ’L’: apply Q or Q**H from the Left;

= ’R’: apply Q or Q**H from the Right.

*UPLO*

UPLO is CHARACTER*1

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

from CHETRD;

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

from CHETRD.

*TRANS*

TRANS is CHARACTER*1

= ’N’: No transpose, apply Q;

= ’C’: Conjugate transpose, apply Q**H.

*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 COMPLEX array, dimension

(LDA,M) if SIDE = ’L’

(LDA,N) if SIDE = ’R’

The vectors which define the elementary reflectors, as

returned by CHETRD.

*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 COMPLEX 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 CHETRD.

*C*

C is 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*

LDC is INTEGER

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

*WORK*

WORK is COMPLEX 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

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

November 2011

Definition at line 172 of file cunmtr.f.

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