---
name: "cunmtr"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/cunmtr/3lapack"
---

# cunmtr(3lapack)

overwrites the general complex M-by-N matrix C with SIDE = 'L' SIDE = 'R' TRANS = 'N'

## NAME

CUNMTR - overwrites 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( \* )

## 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 vectors 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 reflector 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/output) COMPLEX array, dimension (MAX(1,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