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---
:name: claqp2
:md5sum: 44ab7cf5adb154df3f069f835f338c36
:category: :subroutine
:arguments:
- m:
:type: integer
:intent: input
- n:
:type: integer
:intent: input
- offset:
:type: integer
:intent: input
- a:
:type: complex
:intent: input/output
:dims:
- lda
- n
- lda:
:type: integer
:intent: input
- jpvt:
:type: integer
:intent: input/output
:dims:
- n
- tau:
:type: complex
:intent: output
:dims:
- MIN(m,n)
- vn1:
:type: real
:intent: input/output
:dims:
- n
- vn2:
:type: real
:intent: input/output
:dims:
- n
- work:
:type: complex
:intent: workspace
:dims:
- n
:substitutions: {}
:fortran_help: " SUBROUTINE CLAQP2( M, N, OFFSET, A, LDA, JPVT, TAU, VN1, VN2, WORK )\n\n\
* Purpose\n\
* =======\n\
*\n\
* CLAQP2 computes a QR factorization with column pivoting of\n\
* the block A(OFFSET+1:M,1:N).\n\
* The block A(1:OFFSET,1:N) is accordingly pivoted, but not factorized.\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* M (input) INTEGER\n\
* The number of rows of the matrix A. M >= 0.\n\
*\n\
* N (input) INTEGER\n\
* The number of columns of the matrix A. N >= 0.\n\
*\n\
* OFFSET (input) INTEGER\n\
* The number of rows of the matrix A that must be pivoted\n\
* but no factorized. OFFSET >= 0.\n\
*\n\
* A (input/output) COMPLEX array, dimension (LDA,N)\n\
* On entry, the M-by-N matrix A.\n\
* On exit, the upper triangle of block A(OFFSET+1:M,1:N) is \n\
* the triangular factor obtained; the elements in block\n\
* A(OFFSET+1:M,1:N) below the diagonal, together with the\n\
* array TAU, represent the orthogonal matrix Q as a product of\n\
* elementary reflectors. Block A(1:OFFSET,1:N) has been\n\
* accordingly pivoted, but no factorized.\n\
*\n\
* LDA (input) INTEGER\n\
* The leading dimension of the array A. LDA >= max(1,M).\n\
*\n\
* JPVT (input/output) INTEGER array, dimension (N)\n\
* On entry, if JPVT(i) .ne. 0, the i-th column of A is permuted\n\
* to the front of A*P (a leading column); if JPVT(i) = 0,\n\
* the i-th column of A is a free column.\n\
* On exit, if JPVT(i) = k, then the i-th column of A*P\n\
* was the k-th column of A.\n\
*\n\
* TAU (output) COMPLEX array, dimension (min(M,N))\n\
* The scalar factors of the elementary reflectors.\n\
*\n\
* VN1 (input/output) REAL array, dimension (N)\n\
* The vector with the partial column norms.\n\
*\n\
* VN2 (input/output) REAL array, dimension (N)\n\
* The vector with the exact column norms.\n\
*\n\
* WORK (workspace) COMPLEX array, dimension (N)\n\
*\n\n\
* Further Details\n\
* ===============\n\
*\n\
* Based on contributions by\n\
* G. Quintana-Orti, Depto. de Informatica, Universidad Jaime I, Spain\n\
* X. Sun, Computer Science Dept., Duke University, USA\n\
*\n\
* Partial column norm updating strategy modified by\n\
* Z. Drmac and Z. Bujanovic, Dept. of Mathematics,\n\
* University of Zagreb, Croatia.\n\
* June 2010\n\
* For more details see LAPACK Working Note 176.\n\
* =====================================================================\n\
*\n"
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