#include "clapack.h" /* Table of constant values */ static integer c__1 = 1; static integer c_n1 = -1; static integer c__3 = 3; static integer c__2 = 2; /* Subroutine */ int dgeqrf_(integer *m, integer *n, doublereal *a, integer * lda, doublereal *tau, doublereal *work, integer *lwork, integer *info) { /* System generated locals */ integer a_dim1, a_offset, i__1, i__2, i__3, i__4; /* Local variables */ integer i__, k, ib, nb, nx, iws, nbmin, iinfo; extern /* Subroutine */ int dgeqr2_(integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *), dlarfb_(char *, char *, char *, char *, integer *, integer *, integer *, doublereal *, integer *, doublereal *, integer *, doublereal *, integer *, doublereal *, integer *), dlarft_(char *, char *, integer *, integer *, doublereal *, integer *, doublereal *, doublereal *, integer *), xerbla_(char *, integer *); extern integer ilaenv_(integer *, char *, char *, integer *, integer *, integer *, integer *); integer ldwork, lwkopt; logical lquery; /* -- LAPACK routine (version 3.1) -- */ /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ /* November 2006 */ /* .. Scalar Arguments .. */ /* .. */ /* .. Array Arguments .. */ /* .. */ /* Purpose */ /* ======= */ /* DGEQRF computes a QR factorization of a real M-by-N matrix A: */ /* A = Q * R. */ /* Arguments */ /* ========= */ /* M (input) INTEGER */ /* The number of rows of the matrix A. M >= 0. */ /* N (input) INTEGER */ /* The number of columns of the matrix A. N >= 0. */ /* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) */ /* On entry, the M-by-N matrix A. */ /* On exit, the elements on and above the diagonal of the array */ /* contain the min(M,N)-by-N upper trapezoidal matrix R (R is */ /* upper triangular if m >= n); the elements below the diagonal, */ /* with the array TAU, represent the orthogonal matrix Q as a */ /* product of min(m,n) elementary reflectors (see Further */ /* Details). */ /* LDA (input) INTEGER */ /* The leading dimension of the array A. LDA >= max(1,M). */ /* TAU (output) DOUBLE PRECISION array, dimension (min(M,N)) */ /* The scalar factors of the elementary reflectors (see Further */ /* Details). */ /* WORK (workspace/output) DOUBLE PRECISION array, dimension (MAX(1,LWORK)) */ /* On exit, if INFO = 0, WORK(1) returns the optimal LWORK. */ /* LWORK (input) INTEGER */ /* The dimension of the array WORK. LWORK >= max(1,N). */ /* For optimum performance LWORK >= N*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 (output) INTEGER */ /* = 0: successful exit */ /* < 0: if INFO = -i, the i-th argument had an illegal value */ /* 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' */ /* where tau is a real scalar, and v is a real vector with */ /* v(1:i-1) = 0 and v(i) = 1; v(i+1:m) is stored on exit in A(i+1:m,i), */ /* and tau in TAU(i). */ /* ===================================================================== */ /* .. Local Scalars .. */ /* .. */ /* .. External Subroutines .. */ /* .. */ /* .. Intrinsic Functions .. */ /* .. */ /* .. External Functions .. */ /* .. */ /* .. Executable Statements .. */ /* Test the input arguments */ /* Parameter adjustments */ a_dim1 = *lda; a_offset = 1 + a_dim1; a -= a_offset; --tau; --work; /* Function Body */ *info = 0; nb = ilaenv_(&c__1, "DGEQRF", " ", m, n, &c_n1, &c_n1); lwkopt = *n * nb; work[1] = (doublereal) lwkopt; lquery = *lwork == -1; if (*m < 0) { *info = -1; } else if (*n < 0) { *info = -2; } else if (*lda < max(1,*m)) { *info = -4; } else if (*lwork < max(1,*n) && ! lquery) { *info = -7; } if (*info != 0) { i__1 = -(*info); xerbla_("DGEQRF", &i__1); return 0; } else if (lquery) { return 0; } /* Quick return if possible */ k = min(*m,*n); if (k == 0) { work[1] = 1.; return 0; } nbmin = 2; nx = 0; iws = *n; if (nb > 1 && nb < k) { /* Determine when to cross over from blocked to unblocked code. */ /* Computing MAX */ i__1 = 0, i__2 = ilaenv_(&c__3, "DGEQRF", " ", m, n, &c_n1, &c_n1); nx = max(i__1,i__2); if (nx < k) { /* Determine if workspace is large enough for blocked code. */ ldwork = *n; iws = ldwork * nb; if (*lwork < iws) { /* Not enough workspace to use optimal NB: reduce NB and */ /* determine the minimum value of NB. */ nb = *lwork / ldwork; /* Computing MAX */ i__1 = 2, i__2 = ilaenv_(&c__2, "DGEQRF", " ", m, n, &c_n1, & c_n1); nbmin = max(i__1,i__2); } } } if (nb >= nbmin && nb < k && nx < k) { /* Use blocked code initially */ i__1 = k - nx; i__2 = nb; for (i__ = 1; i__2 < 0 ? i__ >= i__1 : i__ <= i__1; i__ += i__2) { /* Computing MIN */ i__3 = k - i__ + 1; ib = min(i__3,nb); /* Compute the QR factorization of the current block */ /* A(i:m,i:i+ib-1) */ i__3 = *m - i__ + 1; dgeqr2_(&i__3, &ib, &a[i__ + i__ * a_dim1], lda, &tau[i__], &work[ 1], &iinfo); if (i__ + ib <= *n) { /* Form the triangular factor of the block reflector */ /* H = H(i) H(i+1) . . . H(i+ib-1) */ i__3 = *m - i__ + 1; dlarft_("Forward", "Columnwise", &i__3, &ib, &a[i__ + i__ * a_dim1], lda, &tau[i__], &work[1], &ldwork); /* Apply H' to A(i:m,i+ib:n) from the left */ i__3 = *m - i__ + 1; i__4 = *n - i__ - ib + 1; dlarfb_("Left", "Transpose", "Forward", "Columnwise", &i__3, & i__4, &ib, &a[i__ + i__ * a_dim1], lda, &work[1], & ldwork, &a[i__ + (i__ + ib) * a_dim1], lda, &work[ib + 1], &ldwork); } /* L10: */ } } else { i__ = 1; } /* Use unblocked code to factor the last or only block. */ if (i__ <= k) { i__2 = *m - i__ + 1; i__1 = *n - i__ + 1; dgeqr2_(&i__2, &i__1, &a[i__ + i__ * a_dim1], lda, &tau[i__], &work[1] , &iinfo); } work[1] = (doublereal) iws; return 0; /* End of DGEQRF */ } /* dgeqrf_ */