org.netlib.lapack
Class Dgeqrf

java.lang.Object
  org.netlib.lapack.Dgeqrf

public class Dgeqrf
extends java.lang.Object

Following is the description from the original
Fortran source.  For each array argument, the Java
version will include an integer offset parameter, so
the arguments may not match the description exactly.
Contact seymour@cs.utk.edu with any questions.


 *     ..
 *
 *  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 (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 ..

Constructor Summary

Dgeqrf()

Method Summary

static void

dgeqrf(int m, int n, double[] a, int _a_offset, int lda, double[] tau, int _tau_offset, double[] work, int _work_offset, int lwork, intW info)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Dgeqrf

public Dgeqrf()

Method Detail

dgeqrf

public static void dgeqrf(int m,
                          int n,
                          double[] a,
                          int _a_offset,
                          int lda,
                          double[] tau,
                          int _tau_offset,
                          double[] work,
                          int _work_offset,
                          int lwork,
                          intW info)