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LAPACK
3.7.0
LAPACK: Linear Algebra PACKage
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subroutine zgelq2 | ( | integer | M, |
integer | N, | ||
complex*16, dimension( lda, * ) | A, | ||
integer | LDA, | ||
complex*16, dimension( * ) | TAU, | ||
complex*16, dimension( * ) | WORK, | ||
integer | INFO | ||
) |
ZGELQ2 computes the LQ factorization of a general rectangular matrix using an unblocked algorithm.
Download ZGELQ2 + dependencies [TGZ] [ZIP] [TXT]
ZGELQ2 computes an LQ factorization of a complex m by n matrix A: A = L * Q.
[in] | M | M is INTEGER The number of rows of the matrix A. M >= 0. |
[in] | N | N is INTEGER The number of columns of the matrix A. N >= 0. |
[in,out] | A | A is COMPLEX*16 array, dimension (LDA,N) On entry, the m by n matrix A. On exit, the elements on and below the diagonal of the array contain the m by min(m,n) lower trapezoidal matrix L (L is lower triangular if m <= n); the elements above the diagonal, with the array TAU, represent the unitary matrix Q as a product of elementary reflectors (see Further Details). |
[in] | LDA | LDA is INTEGER The leading dimension of the array A. LDA >= max(1,M). |
[out] | TAU | TAU is COMPLEX*16 array, dimension (min(M,N)) The scalar factors of the elementary reflectors (see Further Details). |
[out] | WORK | WORK is COMPLEX*16 array, dimension (M) |
[out] | INFO | INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value |
The matrix Q is represented as a product of elementary reflectors Q = H(k)**H . . . H(2)**H H(1)**H, where k = min(m,n). Each H(i) has the form H(i) = I - tau * v * v**H where tau is a complex scalar, and v is a complex vector with v(1:i-1) = 0 and v(i) = 1; conjg(v(i+1:n)) is stored on exit in A(i,i+1:n), and tau in TAU(i).
Definition at line 123 of file zgelq2.f.