LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  dlaqp2 (M, N, OFFSET, A, LDA, JPVT, TAU, VN1, VN2, WORK) 
DLAQP2 computes a QR factorization with column pivoting of the matrix block. 
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 MbyN 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 ith column of A is permuted to the front of A*P (a leading column); if JPVT(i) = 0, the ith column of A is a free column. On exit, if JPVT(i) = k, then the ith column of A*P was the kth 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 149 of file dlaqp2.f.