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dgerqf.f(3) LAPACK dgerqf.f(3) NAME dgerqf.f  SYNOPSIS Functions/Subroutines subroutine dgerqf (M, N, A, LDA, TAU, WORK, LWORK, INFO) DGERQF Function/Subroutine Documentation subroutine dgerqf (integerM, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )TAU, double precision, dimension( * )WORK, integerLWORK, integerINFO) DGERQF Purpose: DGERQF computes an RQ factorization of a real MbyN matrix A: A = R * Q. Parameters: M M is INTEGER The number of rows of the matrix A. M >= 0. N N is INTEGER The number of columns of the matrix A. N >= 0. A A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the MbyN matrix A. On exit, if m <= n, the upper triangle of the subarray A(1:m,nm+1:n) contains the MbyM upper triangular matrix R; if m >= n, the elements on and above the (mn)th subdiagonal contain the MbyN upper trapezoidal matrix R; the remaining elements, with the array TAU, represent the orthogonal matrix Q as a product of min(m,n) elementary reflectors (see Further Details). LDA LDA is INTEGER The leading dimension of the array A. LDA >= max(1,M). TAU TAU is DOUBLE PRECISION array, dimension (min(M,N)) The scalar factors of the elementary reflectors (see Further Details). WORK WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK. LWORK LWORK is INTEGER The dimension of the array WORK. LWORK >= max(1,M). For optimum performance LWORK >= M*NB, where NB is the optimal blocksize. If LWORK = 1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA. INFO INFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value Author: Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd. Date: November 2011 Further Details: The matrix Q is represented as a product of elementary reflectors Q = H(1) H(2) . . . H(k), where k = min(m,n). Each H(i) has the form H(i) = I  tau * v * v**T where tau is a real scalar, and v is a real vector with v(nk+i+1:n) = 0 and v(nk+i) = 1; v(1:nk+i1) is stored on exit in A(mk+i,1:nk+i1), and tau in TAU(i). Definition at line 139 of file dgerqf.f. Author Generated automatically by Doxygen for LAPACK from the source code. Version 3.4.2 Tue Sep 25 2012 dgerqf.f(3)