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---
:name: cgerq2
:md5sum: 5c2737c86fa799ea149918e61f3f15a4
:category: :subroutine
:arguments:
- m:
:type: integer
:intent: input
- n:
:type: integer
:intent: input
- a:
:type: complex
:intent: input/output
:dims:
- lda
- n
- lda:
:type: integer
:intent: input
- tau:
:type: complex
:intent: output
:dims:
- MIN(m,n)
- work:
:type: complex
:intent: workspace
:dims:
- m
- info:
:type: integer
:intent: output
:substitutions:
m: lda
:fortran_help: " SUBROUTINE CGERQ2( M, N, A, LDA, TAU, WORK, INFO )\n\n\
* Purpose\n\
* =======\n\
*\n\
* CGERQ2 computes an RQ factorization of a complex m by n matrix A:\n\
* A = R * Q.\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\
* A (input/output) COMPLEX array, dimension (LDA,N)\n\
* On entry, the m by n matrix A.\n\
* On exit, if m <= n, the upper triangle of the subarray\n\
* A(1:m,n-m+1:n) contains the m by m upper triangular matrix R;\n\
* if m >= n, the elements on and above the (m-n)-th subdiagonal\n\
* contain the m by n upper trapezoidal matrix R; the remaining\n\
* elements, with the array TAU, represent the unitary matrix\n\
* Q as a product of elementary reflectors (see Further\n\
* Details).\n\
*\n\
* LDA (input) INTEGER\n\
* The leading dimension of the array A. LDA >= max(1,M).\n\
*\n\
* TAU (output) COMPLEX array, dimension (min(M,N))\n\
* The scalar factors of the elementary reflectors (see Further\n\
* Details).\n\
*\n\
* WORK (workspace) COMPLEX array, dimension (M)\n\
*\n\
* INFO (output) INTEGER\n\
* = 0: successful exit\n\
* < 0: if INFO = -i, the i-th argument had an illegal value\n\
*\n\n\
* Further Details\n\
* ===============\n\
*\n\
* The matrix Q is represented as a product of elementary reflectors\n\
*\n\
* Q = H(1)' H(2)' . . . H(k)', where k = min(m,n).\n\
*\n\
* Each H(i) has the form\n\
*\n\
* H(i) = I - tau * v * v'\n\
*\n\
* where tau is a complex scalar, and v is a complex vector with\n\
* v(n-k+i+1:n) = 0 and v(n-k+i) = 1; conjg(v(1:n-k+i-1)) is stored on\n\
* exit in A(m-k+i,1:n-k+i-1), and tau in TAU(i).\n\
*\n\
* =====================================================================\n\
*\n"
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