org.netlib.lapack
Class Dbdsdc
java.lang.Object
org.netlib.lapack.Dbdsdc
public class Dbdsdc
- 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
* =======
*
* DBDSDC computes the singular value decomposition (SVD) of a real
* N-by-N (upper or lower) bidiagonal matrix B: B = U * S * VT,
* using a divide and conquer method, where S is a diagonal matrix
* with non-negative diagonal elements (the singular values of B), and
* U and VT are orthogonal matrices of left and right singular vectors,
* respectively. DBDSDC can be used to compute all singular values,
* and optionally, singular vectors or singular vectors in compact form.
*
* This code makes very mild assumptions about floating point
* arithmetic. It will work on machines with a guard digit in
* add/subtract, or on those binary machines without guard digits
* which subtract like the Cray X-MP, Cray Y-MP, Cray C-90, or Cray-2.
* It could conceivably fail on hexadecimal or decimal machines
* without guard digits, but we know of none. See DLASD3 for details.
*
* The code currently call DLASDQ if singular values only are desired.
* However, it can be slightly modified to compute singular values
* using the divide and conquer method.
*
* Arguments
* =========
*
* UPLO (input) CHARACTER*1
* = 'U': B is upper bidiagonal.
* = 'L': B is lower bidiagonal.
*
* COMPQ (input) CHARACTER*1
* Specifies whether singular vectors are to be computed
* as follows:
* = 'N': Compute singular values only;
* = 'P': Compute singular values and compute singular
* vectors in compact form;
* = 'I': Compute singular values and singular vectors.
*
* N (input) INTEGER
* The order of the matrix B. N >= 0.
*
* D (input/output) DOUBLE PRECISION array, dimension (N)
* On entry, the n diagonal elements of the bidiagonal matrix B.
* On exit, if INFO=0, the singular values of B.
*
* E (input/output) DOUBLE PRECISION array, dimension (N)
* On entry, the elements of E contain the offdiagonal
* elements of the bidiagonal matrix whose SVD is desired.
* On exit, E has been destroyed.
*
* U (output) DOUBLE PRECISION array, dimension (LDU,N)
* If COMPQ = 'I', then:
* On exit, if INFO = 0, U contains the left singular vectors
* of the bidiagonal matrix.
* For other values of COMPQ, U is not referenced.
*
* LDU (input) INTEGER
* The leading dimension of the array U. LDU >= 1.
* If singular vectors are desired, then LDU >= max( 1, N ).
*
* VT (output) DOUBLE PRECISION array, dimension (LDVT,N)
* If COMPQ = 'I', then:
* On exit, if INFO = 0, VT' contains the right singular
* vectors of the bidiagonal matrix.
* For other values of COMPQ, VT is not referenced.
*
* LDVT (input) INTEGER
* The leading dimension of the array VT. LDVT >= 1.
* If singular vectors are desired, then LDVT >= max( 1, N ).
*
* Q (output) DOUBLE PRECISION array, dimension (LDQ)
* If COMPQ = 'P', then:
* On exit, if INFO = 0, Q and IQ contain the left
* and right singular vectors in a compact form,
* requiring O(N log N) space instead of 2*N**2.
* In particular, Q contains all the DOUBLE PRECISION data in
* LDQ >= N*(11 + 2*SMLSIZ + 8*INT(LOG_2(N/(SMLSIZ+1))))
* words of memory, where SMLSIZ is returned by ILAENV and
* is equal to the maximum size of the subproblems at the
* bottom of the computation tree (usually about 25).
* For other values of COMPQ, Q is not referenced.
*
* IQ (output) INTEGER array, dimension (LDIQ)
* If COMPQ = 'P', then:
* On exit, if INFO = 0, Q and IQ contain the left
* and right singular vectors in a compact form,
* requiring O(N log N) space instead of 2*N**2.
* In particular, IQ contains all INTEGER data in
* LDIQ >= N*(3 + 3*INT(LOG_2(N/(SMLSIZ+1))))
* words of memory, where SMLSIZ is returned by ILAENV and
* is equal to the maximum size of the subproblems at the
* bottom of the computation tree (usually about 25).
* For other values of COMPQ, IQ is not referenced.
*
* WORK (workspace) DOUBLE PRECISION array, dimension (LWORK)
* If COMPQ = 'N' then LWORK >= (4 * N).
* If COMPQ = 'P' then LWORK >= (6 * N).
* If COMPQ = 'I' then LWORK >= (3 * N**2 + 4 * N).
*
* IWORK (workspace) INTEGER array, dimension (8*N)
*
* INFO (output) INTEGER
* = 0: successful exit.
* < 0: if INFO = -i, the i-th argument had an illegal value.
* > 0: The algorithm failed to compute an singular value.
* The update process of divide and conquer failed.
*
* Further Details
* ===============
*
* Based on contributions by
* Ming Gu and Huan Ren, Computer Science Division, University of
* California at Berkeley, USA
*
* =====================================================================
*
* .. Parameters ..
|
Method Summary |
static void |
dbdsdc(java.lang.String uplo,
java.lang.String compq,
int n,
double[] d,
int _d_offset,
double[] e,
int _e_offset,
double[] u,
int _u_offset,
int ldu,
double[] vt,
int _vt_offset,
int ldvt,
double[] q,
int _q_offset,
int[] iq,
int _iq_offset,
double[] work,
int _work_offset,
int[] iwork,
int _iwork_offset,
intW info)
|
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Dbdsdc
public Dbdsdc()
dbdsdc
public static void dbdsdc(java.lang.String uplo,
java.lang.String compq,
int n,
double[] d,
int _d_offset,
double[] e,
int _e_offset,
double[] u,
int _u_offset,
int ldu,
double[] vt,
int _vt_offset,
int ldvt,
double[] q,
int _q_offset,
int[] iq,
int _iq_offset,
double[] work,
int _work_offset,
int[] iwork,
int _iwork_offset,
intW info)