org.netlib.lapack
Class DGELSY
java.lang.Object
org.netlib.lapack.DGELSY
public class DGELSY
 extends java.lang.Object
DGELSY is a simplified interface to the JLAPACK routine dgelsy.
This interface converts Javastyle 2D rowmajor arrays into
the 1D columnmajor 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
* =======
*
* DGELSY computes the minimumnorm solution to a real linear least
* squares problem:
* minimize  A * X  B 
* using a complete orthogonal factorization of A. A is an MbyN
* matrix which may be rankdeficient.
*
* Several right hand side vectors b and solution vectors x can be
* handled in a single call; they are stored as the columns of the
* MbyNRHS right hand side matrix B and the NbyNRHS solution
* matrix X.
*
* The routine first computes a QR factorization with column pivoting:
* A * P = Q * [ R11 R12 ]
* [ 0 R22 ]
* with R11 defined as the largest leading submatrix whose estimated
* condition number is less than 1/RCOND. The order of R11, RANK,
* is the effective rank of A.
*
* Then, R22 is considered to be negligible, and R12 is annihilated
* by orthogonal transformations from the right, arriving at the
* complete orthogonal factorization:
* A * P = Q * [ T11 0 ] * Z
* [ 0 0 ]
* The minimumnorm solution is then
* X = P * Z' [ inv(T11)*Q1'*B ]
* [ 0 ]
* where Q1 consists of the first RANK columns of Q.
*
* This routine is basically identical to the original xGELSX except
* three differences:
* o The call to the subroutine xGEQPF has been substituted by the
* the call to the subroutine xGEQP3. This subroutine is a Blas3
* version of the QR factorization with column pivoting.
* o Matrix B (the right hand side) is updated with Blas3.
* o The permutation of matrix B (the right hand side) is faster and
* more simple.
*
* 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.
*
* NRHS (input) INTEGER
* The number of right hand sides, i.e., the number of
* columns of matrices B and X. NRHS >= 0.
*
* A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
* On entry, the MbyN matrix A.
* On exit, A has been overwritten by details of its
* complete orthogonal factorization.
*
* LDA (input) INTEGER
* The leading dimension of the array A. LDA >= max(1,M).
*
* B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
* On entry, the MbyNRHS right hand side matrix B.
* On exit, the NbyNRHS solution matrix X.
*
* LDB (input) INTEGER
* The leading dimension of the array B. LDB >= max(1,M,N).
*
* JPVT (input/output) INTEGER array, dimension (N)
* On entry, if JPVT(i) .ne. 0, the ith column of A is permuted
* to the front of AP, otherwise column i is a free column.
* On exit, if JPVT(i) = k, then the ith column of AP
* was the kth column of A.
*
* RCOND (input) DOUBLE PRECISION
* RCOND is used to determine the effective rank of A, which
* is defined as the order of the largest leading triangular
* submatrix R11 in the QR factorization with pivoting of A,
* whose estimated condition number < 1/RCOND.
*
* RANK (output) INTEGER
* The effective rank of A, i.e., the order of the submatrix
* R11. This is the same as the order of the submatrix T11
* in the complete orthogonal factorization of A.
*
* 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.
* The unblocked strategy requires that:
* LWORK >= MAX( MN+3*N+1, 2*MN+NRHS ),
* where MN = min( M, N ).
* The block algorithm requires that:
* LWORK >= MAX( MN+2*N+NB*(N+1), 2*MN+NB*NRHS ),
* where NB is an upper bound on the blocksize returned
* by ILAENV for the routines DGEQP3, DTZRZF, STZRQF, DORMQR,
* and DORMRZ.
*
* 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 ith argument had an illegal value.
*
* Further Details
* ===============
*
* Based on contributions by
* A. Petitet, Computer Science Dept., Univ. of Tenn., Knoxville, USA
* E. QuintanaOrti, Depto. de Informatica, Universidad Jaime I, Spain
* G. QuintanaOrti, Depto. de Informatica, Universidad Jaime I, Spain
*
* =====================================================================
*
* .. Parameters ..
Method Summary 
static void 
DGELSY(int m,
int n,
int nrhs,
double[][] a,
double[][] b,
int[] jpvt,
double rcond,
intW rank,
double[] work,
int lwork,
intW info)

Methods inherited from class java.lang.Object 
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
DGELSY
public DGELSY()
DGELSY
public static void DGELSY(int m,
int n,
int nrhs,
double[][] a,
double[][] b,
int[] jpvt,
double rcond,
intW rank,
double[] work,
int lwork,
intW info)