LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

Go to the source code of this file.
Functions/Subroutines  
subroutine  slaqps (M, N, OFFSET, NB, KB, A, LDA, JPVT, TAU, VN1, VN2, AUXV, F, LDF) 
SLAQPS computes a step of QR factorization with column pivoting of a real mbyn matrix A by using BLAS level 3. 
subroutine slaqps  (  integer  M, 
integer  N,  
integer  OFFSET,  
integer  NB,  
integer  KB,  
real, dimension( lda, * )  A,  
integer  LDA,  
integer, dimension( * )  JPVT,  
real, dimension( * )  TAU,  
real, dimension( * )  VN1,  
real, dimension( * )  VN2,  
real, dimension( * )  AUXV,  
real, dimension( ldf, * )  F,  
integer  LDF  
) 
SLAQPS computes a step of QR factorization with column pivoting of a real mbyn matrix A by using BLAS level 3.
Download SLAQPS + dependencies [TGZ] [ZIP] [TXT]SLAQPS computes a step of QR factorization with column pivoting of a real MbyN matrix A by using Blas3. It tries to factorize NB columns from A starting from the row OFFSET+1, and updates all of the matrix with Blas3 xGEMM. In some cases, due to catastrophic cancellations, it cannot factorize NB columns. Hence, the actual number of factorized columns is returned in KB. 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 A that have been factorized in previous steps. 
[in]  NB  NB is INTEGER The number of columns to factorize. 
[out]  KB  KB is INTEGER The number of columns actually factorized. 
[in,out]  A  A is REAL array, dimension (LDA,N) On entry, the MbyN matrix A. On exit, block A(OFFSET+1:M,1:KB) is the triangular factor obtained and block A(1:OFFSET,1:N) has been accordingly pivoted, but no factorized. The rest of the matrix, block A(OFFSET+1:M,KB+1:N) has been updated. 
[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) JPVT(I) = K <==> Column K of the full matrix A has been permuted into position I in AP. 
[out]  TAU  TAU is REAL array, dimension (KB) The scalar factors of the elementary reflectors. 
[in,out]  VN1  VN1 is REAL array, dimension (N) The vector with the partial column norms. 
[in,out]  VN2  VN2 is REAL array, dimension (N) The vector with the exact column norms. 
[in,out]  AUXV  AUXV is REAL array, dimension (NB) Auxiliar vector. 
[in,out]  F  F is REAL array, dimension (LDF,NB) Matrix F**T = L*Y**T*A. 
[in]  LDF  LDF is INTEGER The leading dimension of the array F. LDF >= max(1,N). 
Partial column norm updating strategy modified on April 2011 Z. Drmac and Z. Bujanovic, Dept. of Mathematics, University of Zagreb, Croatia.
Definition at line 178 of file slaqps.f.