dgelqf dgeqp3 dgeqrf dorglq dorgqr dormlq dormqr

dgeqp3() void dgeqp3 ( int  m, int  n, int  lda, double  a[], int  jpvt[], double  tau[], double  work[], int  lwork, int *  info  ) QR factorization with pivoting Purpose This routine computes a QR factorization with column pivoting of a matrix A: A * P = Q * R using Level 3 BLAS. Parameters [in] m Number of rows of the matrix A. (m >= 0) [in] n Number of columns of the matrix A. (n >= 0) [in] lda Leading dimension of the two dimensional array a[][]. (lda >= max(1, m)) [in,out] a[][] Array a[la][lda] (la >= n) [in] m x n matrix A. [out] The upper triangle of the array contains the min(m, n) x n upper trapezoidal matrix R; the elements below the diagonal, together with the array tau[], represent the orthogonal matrix Q as a product of min(m, n) elementary reflectors. [in,out] jpvt[] Array jpvt[ljpvt] (ljpvt >= n) [in] If jpvt[j-1] != 0, the j-th column of A is permuted to the front of A*P (a leading column); if jpvt[j-1] = 0, the j-th column of A is a free column. [out] If jpvt[j-1] = k, then the j-th column of A*P was the the k-th column of A. [out] tau[] Array tau[ltau] (ltau >= min(m, n)) The scalar factors of the elementary reflectors. [out] work[] Array work[lwork] Work array. On exit, if info = 0, work[0] returns the optimal lwork. [in] lwork The dimension of the array work[]. (lwork >= 3*n + 1) For optimal performance lwork >= 2*n + (n + 1)*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, and returns the value in work[0]. [out] info = 0: Successful exit = -1: The argument m had an illegal value (m < 0) = -2: The argument n had an illegal value (n < 0) = -3: The argument lda had an illegal value (lda < max(1, m)) = -8: The argument lwork had an illegal value (lwork too small) Reference LAPACK