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

# dormlq(3lapack)

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

## NAME

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

## SYNOPSIS

- SUBROUTINE DORMLQ(

  SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO )

- CHARACTER

  SIDE, TRANS

- INTEGER

  INFO, K, LDA, LDC, LWORK, M, N

- DOUBLE

  PRECISION A( LDA, \* ), C( LDC, \* ), TAU( \* ), WORK( \* )

## PURPOSE

DORMLQ overwrites the general real M-by-N matrix C with TRANS = 'T':      Q\*\*T \* C       C \* Q\*\*T\
 where Q is a real orthogonal matrix defined as the product of k elementary reflectors\
\
       Q = H(k) . . . H(2) H(1)\
 as returned by DGELQF. Q is of order M if SIDE = 'L' and of order N if SIDE = 'R'.\

## ARGUMENTS

- SIDE (input) CHARACTER\*1

  \= 'L': apply Q or Q\*\*T from the Left;\
   \= 'R': apply Q or Q\*\*T from the Right.

- TRANS (input) CHARACTER\*1

  \= 'N':  No transpose, apply Q;\
   \= 'T':  Transpose, apply Q\*\*T.

- 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.

- K (input) 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 (input) DOUBLE PRECISION array, dimension

  (LDA,M) if SIDE = 'L', (LDA,N) if SIDE = 'R' The i-th row must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGELQF in the first k rows of its array argument A. A is modified by the routine but restored on exit.

- LDA (input) INTEGER

  The leading dimension of the array A. LDA \>= max(1,K).

- TAU (input) DOUBLE PRECISION array, dimension (K)

  TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by DGELQF.

- C (input/output) 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 (input) INTEGER

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

- WORK (workspace/output) DOUBLE PRECISION 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