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LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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subroutine dlaqp2 | ( | integer | m, |
integer | n, | ||
integer | offset, | ||
double precision, dimension( lda, * ) | a, | ||
integer | lda, | ||
integer, dimension( * ) | jpvt, | ||
double precision, dimension( * ) | tau, | ||
double precision, dimension( * ) | vn1, | ||
double precision, dimension( * ) | vn2, | ||
double precision, dimension( * ) | work | ||
) |
DLAQP2 computes a QR factorization with column pivoting of the matrix block.
Download DLAQP2 + dependencies [TGZ] [ZIP] [TXT]
DLAQP2 computes a QR factorization with column pivoting of the block A(OFFSET+1:M,1:N). The block A(1:OFFSET,1:N) is accordingly pivoted, but not factorized.
[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] | OFFSET | OFFSET is INTEGER The number of rows of the matrix A that must be pivoted but no factorized. OFFSET >= 0. |
[in,out] | A | A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the M-by-N matrix A. On exit, the upper triangle of block A(OFFSET+1:M,1:N) is the triangular factor obtained; the elements in block A(OFFSET+1:M,1:N) below the diagonal, together with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. Block A(1:OFFSET,1:N) has been accordingly pivoted, but no factorized. |
[in] | LDA | LDA is INTEGER The leading dimension of the array A. LDA >= max(1,M). |
[in,out] | JPVT | JPVT is INTEGER array, dimension (N) On entry, if JPVT(i) .ne. 0, the i-th column of A is permuted to the front of A*P (a leading column); if JPVT(i) = 0, the i-th column of A is a free column. On exit, if JPVT(i) = k, then the i-th column of A*P was the k-th column of A. |
[out] | TAU | TAU is DOUBLE PRECISION array, dimension (min(M,N)) The scalar factors of the elementary reflectors. |
[in,out] | VN1 | VN1 is DOUBLE PRECISION array, dimension (N) The vector with the partial column norms. |
[in,out] | VN2 | VN2 is DOUBLE PRECISION array, dimension (N) The vector with the exact column norms. |
[out] | WORK | WORK is DOUBLE PRECISION array, dimension (N) |
Definition at line 147 of file dlaqp2.f.