sormqr (l)  Linux Man Pages
sormqr: overwrites the general real MbyN matrix C with SIDE = aqLaq SIDE = aqRaq TRANS = aqNaq
NAME
SORMQR  overwrites the general real MbyN matrix C with SIDE = aqLaq SIDE = aqRaq TRANS = aqNaqSYNOPSIS
 SUBROUTINE SORMQR(
 SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO )
 CHARACTER SIDE, TRANS
 INTEGER INFO, K, LDA, LDC, LWORK, M, N
 REAL A( LDA, * ), C( LDC, * ), TAU( * ), WORK( * )
PURPOSE
SORMQR 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 SGEQRF. 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) REAL 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 SGEQRF 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) REAL array, dimension (K)
 TAU(i) must contain the scalar factor of the elementary reflector H(i), as returned by SGEQRF.
 C (input/output) REAL 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) REAL 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