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

# dormql(3lapack)

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

## NAME

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

## SYNOPSIS

- SUBROUTINE DORMQL(

  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

DORMQL 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 DGEQLF. 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,K)

  The i-th column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGEQLF in the last k columns 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. If SIDE = 'L', LDA \>= max(1,M); if SIDE = 'R', LDA \>= max(1,N).

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

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

- 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