dormqr (l)  Linux Manuals
dormqr: overwrites the general real MbyN matrix C with SIDE = aqLaq SIDE = aqRaq TRANS = aqNaq
NAME
DORMQR  overwrites the general real MbyN matrix C with SIDE = aqLaq SIDE = aqRaq TRANS = aqNaqSYNOPSIS
 SUBROUTINE DORMQR(
 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
DORMQR overwrites the general real MbyN matrix C with TRANS = aqTaq: Q**T * C C * Q**Twhere Q is a real orthogonal matrix defined as the product of k elementary reflectors
Q
as returned by DGEQRF. Q is of order M if SIDE = aqLaq and of order N if SIDE = aqRaq.
ARGUMENTS
 SIDE (input) CHARACTER*1

= aqLaq: apply Q or Q**T from the Left;
= aqRaq: apply Q or Q**T from the Right.  TRANS (input) CHARACTER*1

= aqNaq: No transpose, apply Q;
= aqTaq: 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 = aqLaq, M >= K >= 0; if SIDE = aqRaq, N >= K >= 0.
 A (input) DOUBLE PRECISION array, dimension (LDA,K)
 The ith column must contain the vector which defines the elementary reflector H(i), for i = 1,2,...,k, as returned by DGEQRF in the first 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 = aqLaq, LDA >= max(1,M); if SIDE = aqRaq, 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 DGEQRF.
 C (input/output) DOUBLE PRECISION array, dimension (LDC,N)
 On entry, the MbyN 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 = aqLaq, LWORK >= max(1,N); if SIDE = aqRaq, LWORK >= max(1,M). For optimum performance LWORK >= N*NB if SIDE = aqLaq, and LWORK >= M*NB if SIDE = aqRaq, 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 ith argument had an illegal value