redhat man page for zgeqrf

Query: zgeqrf

OS: redhat

Section: l

Format: Original Unix Latex Style Formatted with HTML and a Horizontal Scroll Bar

ZGEQRF(l)								 )								 ZGEQRF(l)

NAME
ZGEQRF - compute a QR factorization of a complex M-by-N matrix A
SYNOPSIS
SUBROUTINE ZGEQRF( M, N, A, LDA, TAU, WORK, LWORK, INFO ) INTEGER INFO, LDA, LWORK, M, N COMPLEX*16 A( LDA, * ), TAU( * ), WORK( * )
PURPOSE
ZGEQRF computes a QR factorization of a complex M-by-N matrix A: A = Q * R.
ARGUMENTS
M (input) INTEGER The number of rows of the matrix A. M >= 0. N (input) INTEGER The number of columns of the matrix A. N >= 0. A (input/output) COMPLEX*16 array, dimension (LDA,N) On entry, the M-by-N matrix A. On exit, the elements on and above the diagonal of the array contain the min(M,N)-by-N upper trape- zoidal matrix R (R is upper triangular if m >= n); the elements below the diagonal, with the array TAU, represent the unitary matrix Q as a product of min(m,n) elementary reflectors (see Further Details). LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,M). TAU (output) COMPLEX*16 array, dimension (min(M,N)) The scalar factors of the elementary reflectors (see Further Details). WORK (workspace/output) COMPLEX*16 array, dimension (LWORK) On exit, if INFO = 0, WORK(1) returns the optimal LWORK. LWORK (input) INTEGER The dimension of the array WORK. LWORK >= max(1,N). For optimum performance LWORK >= N*NB, 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
FURTHER DETAILS
The matrix Q is represented as a product of elementary reflectors Q = H(1) H(2) . . . H(k), where k = min(m,n). Each H(i) has the form H(i) = I - tau * v * v' where tau is a complex scalar, and v is a complex vector with v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i), and tau in TAU(i). LAPACK version 3.0 15 June 2000 ZGEQRF(l)
Related Man Pages
zungqr(l) - redhat
cgelqf(l) - redhat
zgelqf(l) - redhat
zgeqrf(l) - redhat
zgerqf(l) - redhat
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