cunm2r.f −

**Functions/Subroutines**

subroutine **cunm2r** (SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, INFO)

CUNM2R*multiplies a general matrix by the unitary matrix from a QR factorization determined by cgeqrf (unblocked algorithm).*

* subroutine cunm2r (characterSIDE, characterTRANS, integerM, integerN, integerK, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( ldc, * )C, integerLDC, complex, dimension( * )WORK, integerINFO)* multiplies a general matrix by the unitary matrix from a QR factorization determined by cgeqrf (unblocked algorithm).

CUNM2R

**Purpose:**

CUNM2R overwrites the general complex m-by-n matrix C with

Q * C if SIDE = ’L’ and TRANS = ’N’, or

Q**H* C if SIDE = ’L’ and TRANS = ’C’, or

C * Q if SIDE = ’R’ and TRANS = ’N’, or

C * Q**H if SIDE = ’R’ and TRANS = ’C’,

where Q is a complex unitary matrix defined as the product of k

elementary reflectors

as returned by CGEQRF. Q is of order m if SIDE = ’L’ and of order n

if SIDE = ’R’.

**Parameters:**

*SIDE*

SIDE is CHARACTER*1

= ’L’: apply Q or Q**H from the Left

= ’R’: apply Q or Q**H from the Right

*TRANS*

TRANS is CHARACTER*1

= ’N’: apply Q (No transpose)

= ’C’: apply Q**H (Conjugate transpose)

*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.

*K*

K is INTEGER

The number of elementary reflectors whose product defines

the matrix Q.

If SIDE = ’L’, M >= K >= 0;

if SIDE = ’R’, N >= K >= 0.

*A*

A is COMPLEX array, dimension (LDA,K)

The i-th column must contain the vector which defines the

elementary reflector H(i), for i = 1,2,...,k, as returned by

CGEQRF in the first k columns of its array argument A.

A is modified by the routine but restored on exit.

*LDA*

LDA is INTEGER

The leading dimension of the array A.

If SIDE = ’L’, LDA >= max(1,M);

if SIDE = ’R’, LDA >= max(1,N).

*TAU*

TAU is COMPLEX array, dimension (K)

TAU(i) must contain the scalar factor of the elementary

reflector H(i), as returned by CGEQRF.

*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

(N) if SIDE = ’L’,

(M) if SIDE = ’R’

*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:**

September 2012

Definition at line 159 of file cunm2r.f.

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