org.netlib.lapack
Class SGGRQF
java.lang.Object
org.netlib.lapack.SGGRQF
public class SGGRQF
- extends java.lang.Object
SGGRQF is a simplified interface to the JLAPACK routine sggrqf.
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
* =======
*
* SGGRQF computes a generalized RQ factorization of an M-by-N matrix A
* and a P-by-N matrix B:
*
* A = R*Q, B = Z*T*Q,
*
* where Q is an N-by-N orthogonal matrix, Z is a P-by-P orthogonal
* matrix, and R and T assume one of the forms:
*
* if M <= N, R = ( 0 R12 ) M, or if M > N, R = ( R11 ) M-N,
* N-M M ( R21 ) N
* N
*
* where R12 or R21 is upper triangular, and
*
* if P >= N, T = ( T11 ) N , or if P < N, T = ( T11 T12 ) P,
* ( 0 ) P-N P N-P
* N
*
* where T11 is upper triangular.
*
* In particular, if B is square and nonsingular, the GRQ factorization
* of A and B implicitly gives the RQ factorization of A*inv(B):
*
* A*inv(B) = (R*inv(T))*Z'
*
* where inv(B) denotes the inverse of the matrix B, and Z' denotes the
* transpose of the matrix Z.
*
* Arguments
* =========
*
* M (input) INTEGER
* The number of rows of the matrix A. M >= 0.
*
* P (input) INTEGER
* The number of rows of the matrix B. P >= 0.
*
* N (input) INTEGER
* The number of columns of the matrices A and B. N >= 0.
*
* A (input/output) REAL 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 TAUA, represent the orthogonal
* matrix Q as a product of elementary reflectors (see Further
* Details).
*
* LDA (input) INTEGER
* The leading dimension of the array A. LDA >= max(1,M).
*
* TAUA (output) REAL array, dimension (min(M,N))
* The scalar factors of the elementary reflectors which
* represent the orthogonal matrix Q (see Further Details).
*
* B (input/output) REAL array, dimension (LDB,N)
* On entry, the P-by-N matrix B.
* On exit, the elements on and above the diagonal of the array
* contain the min(P,N)-by-N upper trapezoidal matrix T (T is
* upper triangular if P >= N); the elements below the diagonal,
* with the array TAUB, represent the orthogonal matrix Z as a
* product of elementary reflectors (see Further Details).
*
* LDB (input) INTEGER
* The leading dimension of the array B. LDB >= max(1,P).
*
* TAUB (output) REAL array, dimension (min(P,N))
* The scalar factors of the elementary reflectors which
* represent the orthogonal matrix Z (see Further Details).
*
* WORK (workspace/output) REAL 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,M,P).
* For optimum performance LWORK >= max(N,M,P)*max(NB1,NB2,NB3),
* where NB1 is the optimal blocksize for the RQ factorization
* of an M-by-N matrix, NB2 is the optimal blocksize for the
* QR factorization of a P-by-N matrix, and NB3 is the optimal
* blocksize for a call of SORMRQ.
*
* 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 INF0= -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 - taua * v * v'
*
* where taua 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 taua in TAUA(i).
* To form Q explicitly, use LAPACK subroutine SORGRQ.
* To use Q to update another matrix, use LAPACK subroutine SORMRQ.
*
* The matrix Z is represented as a product of elementary reflectors
*
* Z = H(1) H(2) . . . H(k), where k = min(p,n).
*
* Each H(i) has the form
*
* H(i) = I - taub * v * v'
*
* where taub is a real scalar, and v is a real vector with
* v(1:i-1) = 0 and v(i) = 1; v(i+1:p) is stored on exit in B(i+1:p,i),
* and taub in TAUB(i).
* To form Z explicitly, use LAPACK subroutine SORGQR.
* To use Z to update another matrix, use LAPACK subroutine SORMQR.
*
* =====================================================================
*
* .. Local Scalars ..
|
Method Summary |
static void |
SGGRQF(int m,
int p,
int n,
float[][] a,
float[] taua,
float[][] b,
float[] taub,
float[] work,
int lwork,
intW info)
|
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
SGGRQF
public SGGRQF()
SGGRQF
public static void SGGRQF(int m,
int p,
int n,
float[][] a,
float[] taua,
float[][] b,
float[] taub,
float[] work,
int lwork,
intW info)