org.netlib.lapack
Class DGERQF

java.lang.Object
  extended by org.netlib.lapack.DGERQF

public class DGERQF
extends java.lang.Object

DGERQF is a simplified interface to the JLAPACK routine dgerqf.
This interface converts Java-style 2D row-major arrays into
the 1D column-major linearized arrays expected by the lower
level JLAPACK routines.  Using this interface also allows you
to omit offset and leading dimension arguments.  However, because
of these conversions, these routines will be slower than the low
level ones.  Following is the description from the original Fortran
source.  Contact seymour@cs.utk.edu with any questions.

* .. * * Purpose * ======= * * DGERQF computes an RQ factorization of a real M-by-N matrix A: * A = R * Q. * * 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, * if m <= n, the upper triangle of the subarray * A(1:m,n-m+1:n) contains the M-by-M upper triangular matrix R; * if m >= n, the elements on and above the (m-n)-th subdiagonal * contain the M-by-N 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 (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 (LWORK) * On exit, if INFO = 0, WORK(1) returns the optimal LWORK. * * LWORK (input) 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 (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(n-k+i+1:n) = 0 and v(n-k+i) = 1; v(1:n-k+i-1) is stored on exit in * A(m-k+i,1:n-k+i-1), and tau in TAU(i). * * ===================================================================== * * .. Local Scalars ..


Constructor Summary
DGERQF()
           
 
Method Summary
static void DGERQF(int m, int n, double[][] a, double[] tau, double[] work, int lwork, intW info)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DGERQF

public DGERQF()
Method Detail

DGERQF

public static void DGERQF(int m,
                          int n,
                          double[][] a,
                          double[] tau,
                          double[] work,
                          int lwork,
                          intW info)